diff --git a/lib/plausible/auth/invitation.ex b/lib/plausible/auth/invitation.ex
index 5a24b11ba..d0a2eb70f 100644
--- a/lib/plausible/auth/invitation.ex
+++ b/lib/plausible/auth/invitation.ex
@@ -2,6 +2,8 @@ defmodule Plausible.Auth.Invitation do
   use Ecto.Schema
   import Ecto.Changeset
 
+  @type t() :: %__MODULE__{}
+
   @derive {Jason.Encoder, only: [:invitation_id, :role, :site]}
   @required [:email, :role, :site_id, :inviter_id]
   schema "invitations" do
diff --git a/lib/plausible/billing/plans.ex b/lib/plausible/billing/plans.ex
index 6effc2b4b..704a75ca1 100644
--- a/lib/plausible/billing/plans.ex
+++ b/lib/plausible/billing/plans.ex
@@ -2,7 +2,7 @@ defmodule Plausible.Billing.Plan do
   @moduledoc false
 
   @derive Jason.Encoder
-  @enforce_keys ~w(kind site_limit monthly_pageview_limit volume monthly_cost yearly_cost monthly_product_id yearly_product_id)a
+  @enforce_keys ~w(kind site_limit monthly_pageview_limit team_member_limit volume monthly_cost yearly_cost monthly_product_id yearly_product_id)a
   defstruct @enforce_keys
 
   @type t() ::
@@ -10,6 +10,7 @@ defmodule Plausible.Billing.Plan do
             kind: atom(),
             monthly_pageview_limit: non_neg_integer(),
             site_limit: non_neg_integer(),
+            team_member_limit: non_neg_integer() | :unlimited,
             volume: String.t(),
             monthly_cost: String.t() | nil,
             yearly_cost: String.t() | nil,
@@ -36,15 +37,22 @@ defmodule Plausible.Billing.Plans do
       path
       |> File.read!()
       |> Jason.decode!(keys: :atoms!)
-      |> Enum.map(
-        &Map.put(
-          &1,
-          :volume,
-          PlausibleWeb.StatsView.large_number_format(&1.monthly_pageview_limit)
-        )
-      )
-      |> Enum.map(&Map.put(&1, :kind, String.to_atom(&1.kind)))
-      |> Enum.map(&struct!(Plausible.Billing.Plan, &1))
+      |> Enum.map(fn raw ->
+        team_member_limit =
+          case raw.team_member_limit do
+            number when is_integer(number) -> number
+            "unlimited" -> :unlimited
+            _any -> raise ArgumentError, "Failed to parse team member limit from plan JSON files"
+          end
+
+        volume = PlausibleWeb.StatsView.large_number_format(raw.monthly_pageview_limit)
+
+        raw
+        |> Map.put(:volume, volume)
+        |> Map.put(:kind, String.to_atom(raw.kind))
+        |> Map.put(:team_member_limit, team_member_limit)
+        |> then(&struct!(Plausible.Billing.Plan, &1))
+      end)
 
     Module.put_attribute(__MODULE__, f, contents)
     Module.put_attribute(__MODULE__, :external_resource, path)
diff --git a/lib/plausible/billing/quota.ex b/lib/plausible/billing/quota.ex
index bb5250bfc..94b5f080f 100644
--- a/lib/plausible/billing/quota.ex
+++ b/lib/plausible/billing/quota.ex
@@ -3,6 +3,7 @@ defmodule Plausible.Billing.Quota do
   This module provides functions to work with plans usage and limits.
   """
 
+  import Ecto.Query
   alias Plausible.Billing.Plans
 
   @limit_sites_since ~D[2021-05-05]
@@ -79,6 +80,55 @@ defmodule Plausible.Billing.Quota do
     |> Tuple.sum()
   end
 
+  @team_member_limit_for_trials 5
+  @spec team_member_limit(Plausible.Auth.User.t()) :: non_neg_integer()
+  @doc """
+  Returns the limit of team members a user can have in their sites.
+  """
+  def team_member_limit(user) do
+    user = Plausible.Users.with_subscription(user)
+
+    case Plans.get_subscription_plan(user.subscription) do
+      %Plausible.Billing.EnterprisePlan{} -> :unlimited
+      %Plausible.Billing.Plan{team_member_limit: limit} -> limit
+      :free_10k -> :unlimited
+      nil -> @team_member_limit_for_trials
+    end
+  end
+
+  @spec team_member_usage(Plausible.Auth.User.t()) :: integer()
+  @doc """
+  Returns the total count of team members and pending invitations associated
+  with the user's sites.
+  """
+  def team_member_usage(user) do
+    owned_sites_query =
+      from sm in Plausible.Site.Membership,
+        where: sm.role == :owner and sm.user_id == ^user.id,
+        select: %{site_id: sm.site_id}
+
+    team_members_query =
+      from os in subquery(owned_sites_query),
+        inner_join: sm in Plausible.Site.Membership,
+        on: sm.site_id == os.site_id,
+        inner_join: u in assoc(sm, :user),
+        select: %{email: u.email}
+
+    invitations_and_team_members_query =
+      from i in Plausible.Auth.Invitation,
+        inner_join: os in subquery(owned_sites_query),
+        on: i.site_id == os.site_id,
+        select: %{email: i.email},
+        union: ^team_members_query
+
+    query =
+      from itm in subquery(invitations_and_team_members_query),
+        where: itm.email != ^user.email,
+        select: count(itm.email, :distinct)
+
+    Plausible.Repo.one(query)
+  end
+
   @spec within_limit?(non_neg_integer(), non_neg_integer() | :unlimited) :: boolean()
   @doc """
   Returns whether the limit has been exceeded or not.
diff --git a/lib/plausible/sites.ex b/lib/plausible/sites.ex
index 122e086fa..66f39f8d3 100644
--- a/lib/plausible/sites.ex
+++ b/lib/plausible/sites.ex
@@ -49,6 +49,57 @@ defmodule Plausible.Sites do
     end
   end
 
+  @spec invite(Site.t(), Plausible.Auth.User.t(), String.t(), atom()) ::
+          {:ok, Plausible.Auth.Invitation.t()}
+          | {:error, Ecto.Changeset.t()}
+          | {:error, :already_a_member}
+          | {:error, {:over_limit, non_neg_integer()}}
+  def invite(site, inviter, invitee_email, role) do
+    Repo.transaction(fn ->
+      do_invite(site, inviter, invitee_email, role)
+    end)
+  end
+
+  defp do_invite(site, inviter, invitee_email, role) do
+    send_invitation_email = fn invitation, invitee ->
+      invitation = Repo.preload(invitation, [:site, :inviter])
+
+      email =
+        if invitee,
+          do: PlausibleWeb.Email.existing_user_invitation(invitation),
+          else: PlausibleWeb.Email.new_user_invitation(invitation)
+
+      Plausible.Mailer.send(email)
+    end
+
+    ensure_new_membership = fn site, invitee ->
+      if invitee && is_member?(invitee.id, site), do: {:error, :already_a_member}, else: :ok
+    end
+
+    check_limit = fn site ->
+      owner = owner_for(site)
+      usage = Plausible.Billing.Quota.team_member_usage(owner)
+      limit = Plausible.Billing.Quota.team_member_limit(owner)
+
+      if Plausible.Billing.Quota.within_limit?(usage, limit),
+        do: :ok,
+        else: {:error, {:over_limit, limit}}
+    end
+
+    attrs = %{email: invitee_email, role: role, site_id: site.id, inviter_id: inviter.id}
+
+    with :ok <- check_limit.(site),
+         invitee <- Plausible.Auth.find_user_by(email: invitee_email),
+         :ok <- ensure_new_membership.(site, invitee),
+         %Ecto.Changeset{} = changeset <- Plausible.Auth.Invitation.new(attrs),
+         {:ok, invitation} <- Repo.insert(changeset) do
+      send_invitation_email.(invitation, invitee)
+      invitation
+    else
+      {:error, cause} -> Repo.rollback(cause)
+    end
+  end
+
   @spec stats_start_date(Plausible.Site.t()) :: Date.t() | nil
   @doc """
   Returns the date of the first event of the given site, or `nil` if the site
diff --git a/lib/plausible_web/components/billing.ex b/lib/plausible_web/components/billing.ex
index fdb5724f1..b97a9d4a0 100644
--- a/lib/plausible_web/components/billing.ex
+++ b/lib/plausible_web/components/billing.ex
@@ -27,10 +27,18 @@ defmodule PlausibleWeb.Components.Billing do
     <tr {@rest}>
       <td class={["py-4 text-sm whitespace-nowrap text-left", @pad && "pl-6"]}><%= @title %></td>
       <td class="py-4 text-sm whitespace-nowrap text-right">
-        <%= Cldr.Number.to_string!(@usage) %>
-        <%= if is_number(@limit), do: "/ #{Cldr.Number.to_string!(@limit)}" %>
+        <%= render_quota(@usage) %>
+        <%= if @limit, do: "/ #{render_quota(@limit)}" %>
       </td>
     </tr>
     """
   end
+
+  defp render_quota(quota) do
+    case quota do
+      quota when is_number(quota) -> Cldr.Number.to_string!(quota)
+      :unlimited -> "∞"
+      nil -> ""
+    end
+  end
 end
diff --git a/lib/plausible_web/controllers/auth_controller.ex b/lib/plausible_web/controllers/auth_controller.ex
index 416fe6101..5d44be0f2 100644
--- a/lib/plausible_web/controllers/auth_controller.ex
+++ b/lib/plausible_web/controllers/auth_controller.ex
@@ -498,6 +498,8 @@ defmodule PlausibleWeb.AuthController do
       subscription: user.subscription,
       invoices: Plausible.Billing.paddle_api().get_invoices(user.subscription),
       theme: user.theme || "system",
+      team_member_limit: Plausible.Billing.Quota.team_member_limit(user),
+      team_member_usage: Plausible.Billing.Quota.team_member_usage(user),
       site_limit: Plausible.Billing.Quota.site_limit(user),
       site_usage: Plausible.Billing.Quota.site_usage(user),
       total_pageview_limit: Plausible.Billing.Quota.monthly_pageview_limit(user.subscription),
diff --git a/lib/plausible_web/controllers/site/membership_controller.ex b/lib/plausible_web/controllers/site/membership_controller.ex
index aed8b695e..ae721ee4f 100644
--- a/lib/plausible_web/controllers/site/membership_controller.ex
+++ b/lib/plausible_web/controllers/site/membership_controller.ex
@@ -39,62 +39,46 @@ defmodule PlausibleWeb.Site.MembershipController do
   def invite_member(conn, %{"email" => email, "role" => role}) do
     site_domain = conn.assigns[:site].domain
     site = Sites.get_for_user!(conn.assigns[:current_user].id, site_domain)
-    user = Plausible.Auth.find_user_by(email: email)
 
-    if user && Sites.is_member?(user.id, site) do
-      msg = "Cannot send invite because #{user.email} is already a member of #{site.domain}"
+    case Sites.invite(site, conn.assigns.current_user, email, role) do
+      {:ok, invitation} ->
+        conn
+        |> put_flash(
+          :success,
+          "#{email} has been invited to #{site_domain} as #{PlausibleWeb.SiteView.with_indefinite_article("#{invitation.role}")}"
+        )
+        |> redirect(to: Routes.site_path(conn, :settings_people, site.domain))
 
-      render(conn, "invite_member_form.html",
-        error: msg,
-        site: site,
-        layout: {PlausibleWeb.LayoutView, "focus.html"},
-        skip_plausible_tracking: true
-      )
-    else
-      case Repo.insert(
-             Invitation.new(%{
-               email: email,
-               role: role,
-               site_id: site.id,
-               inviter_id: conn.assigns[:current_user].id
-             })
-           ) do
-        {:ok, invitation} ->
-          invitation = Repo.preload(invitation, [:site, :inviter])
+      {:error, :already_a_member} ->
+        render(conn, "invite_member_form.html",
+          error: "Cannot send invite because #{email} is already a member of #{site.domain}",
+          site: site,
+          layout: {PlausibleWeb.LayoutView, "focus.html"},
+          skip_plausible_tracking: true
+        )
 
-          email_template =
-            if user do
-              PlausibleWeb.Email.existing_user_invitation(invitation)
-            else
-              PlausibleWeb.Email.new_user_invitation(invitation)
-            end
+      {:error, {:over_limit, limit}} ->
+        render(conn, "invite_member_form.html",
+          error:
+            "Your account is limited to #{limit} team members. You can upgrade your plan to increase this limit.",
+          site: site,
+          layout: {PlausibleWeb.LayoutView, "focus.html"},
+          skip_plausible_tracking: true
+        )
 
-          Plausible.Mailer.send(email_template)
+      {:error, %Ecto.Changeset{} = changeset} ->
+        error_msg =
+          case changeset.errors[:invitation] do
+            {"already sent", _} ->
+              "This invitation has been already sent. To send again, remove it from pending invitations first."
 
-          conn
-          |> put_flash(
-            :success,
-            "#{email} has been invited to #{site_domain} as #{PlausibleWeb.SiteView.with_indefinite_article(role)}"
-          )
-          |> redirect(to: Routes.site_path(conn, :settings_people, site.domain))
+            _ ->
+              "Something went wrong."
+          end
 
-        {:error, changeset} ->
-          error_msg =
-            case changeset.errors[:invitation] do
-              {"already sent", _} ->
-                "This invitation has been already sent. To send again, remove it from pending invitations first."
-
-              _ ->
-                "Something went wrong."
-            end
-
-          conn
-          |> put_flash(
-            :error,
-            error_msg
-          )
-          |> redirect(to: Routes.site_path(conn, :settings_people, site.domain))
-      end
+        conn
+        |> put_flash(:error, error_msg)
+        |> redirect(to: Routes.site_path(conn, :settings_people, site.domain))
     end
   end
 
diff --git a/lib/plausible_web/templates/auth/user_settings.html.heex b/lib/plausible_web/templates/auth/user_settings.html.heex
index c54352634..289bc91a5 100644
--- a/lib/plausible_web/templates/auth/user_settings.html.heex
+++ b/lib/plausible_web/templates/auth/user_settings.html.heex
@@ -151,6 +151,11 @@
           usage={@site_usage}
           limit={@site_limit}
         />
+        <PlausibleWeb.Components.Billing.usage_and_limits_row
+          title="Team members"
+          usage={@team_member_usage}
+          limit={@team_member_limit}
+        />
       </PlausibleWeb.Components.Billing.usage_and_limits_table>
     </article>
 
diff --git a/priv/plans_v1.json b/priv/plans_v1.json
index 9673f5637..4cfe094f5 100644
--- a/priv/plans_v1.json
+++ b/priv/plans_v1.json
@@ -6,7 +6,8 @@
     "monthly_product_id":"558018",
     "yearly_cost":"$48",
     "yearly_product_id":"572810",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -15,7 +16,8 @@
     "monthly_product_id":"558745",
     "yearly_cost":"$96",
     "yearly_product_id":"590752",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -24,7 +26,8 @@
     "monthly_product_id":"597485",
     "yearly_cost":"$144",
     "yearly_product_id":"597486",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -33,7 +36,8 @@
     "monthly_product_id":"597487",
     "yearly_cost":"$216",
     "yearly_product_id":"597488",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -42,7 +46,8 @@
     "monthly_product_id":"597642",
     "yearly_cost":"$384",
     "yearly_product_id":"597643",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -51,7 +56,8 @@
     "monthly_product_id":"597309",
     "yearly_cost":"$552",
     "yearly_product_id":"597310",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -60,7 +66,8 @@
     "monthly_product_id":"597311",
     "yearly_cost":"$792",
     "yearly_product_id":"597312",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -69,7 +76,8 @@
     "monthly_product_id":"642352",
     "yearly_cost":"$1200",
     "yearly_product_id":"642354",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -78,7 +86,8 @@
     "monthly_product_id":"642355",
     "yearly_cost":"$1800",
     "yearly_product_id":"642356",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -87,6 +96,7 @@
     "monthly_product_id":"650652",
     "yearly_cost":"$2640",
     "yearly_product_id":"650653",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   }
 ]
diff --git a/priv/plans_v2.json b/priv/plans_v2.json
index c6d193bed..d3643daf4 100644
--- a/priv/plans_v2.json
+++ b/priv/plans_v2.json
@@ -6,7 +6,8 @@
     "monthly_product_id":"654177",
     "yearly_cost":"$60",
     "yearly_product_id":"653232",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -15,7 +16,8 @@
     "monthly_product_id":"654178",
     "yearly_cost":"$120",
     "yearly_product_id":"653234",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -24,7 +26,8 @@
     "monthly_product_id":"653237",
     "yearly_cost":"$200",
     "yearly_product_id":"653236",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -33,7 +36,8 @@
     "monthly_product_id":"653238",
     "yearly_cost":"$300",
     "yearly_product_id":"653239",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -42,7 +46,8 @@
     "monthly_product_id":"653240",
     "yearly_cost":"$500",
     "yearly_product_id":"653242",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -51,7 +56,8 @@
     "monthly_product_id":"653253",
     "yearly_cost":"$700",
     "yearly_product_id":"653254",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -60,7 +66,8 @@
     "monthly_product_id":"653255",
     "yearly_cost":"$1000",
     "yearly_product_id":"653256",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -69,7 +76,8 @@
     "monthly_product_id":"654181",
     "yearly_cost":"$1500",
     "yearly_product_id":"653257",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -78,7 +86,8 @@
     "monthly_product_id":"654182",
     "yearly_cost":"$2250",
     "yearly_product_id":"653258",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -87,6 +96,7 @@
     "monthly_product_id":"654183",
     "yearly_cost":"$3300",
     "yearly_product_id":"653259",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   }
 ]
diff --git a/priv/plans_v3.json b/priv/plans_v3.json
index c6677d3b7..3fa6d0736 100644
--- a/priv/plans_v3.json
+++ b/priv/plans_v3.json
@@ -6,7 +6,8 @@
     "monthly_product_id":"749342",
     "yearly_cost":"$90",
     "yearly_product_id":"749343",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -15,7 +16,8 @@
     "monthly_product_id":"749344",
     "yearly_cost":"$190",
     "yearly_product_id":"749345",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -24,7 +26,8 @@
     "monthly_product_id":"749346",
     "yearly_cost":"$290",
     "yearly_product_id":"749347",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -33,7 +36,8 @@
     "monthly_product_id":"749348",
     "yearly_cost":"$490",
     "yearly_product_id":"749349",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -42,7 +46,8 @@
     "monthly_product_id":"749350",
     "yearly_cost":"$690",
     "yearly_product_id":"749352",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -51,7 +56,8 @@
     "monthly_product_id":"749353",
     "yearly_cost":"$890",
     "yearly_product_id":"749355",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -60,7 +66,8 @@
     "monthly_product_id":"749356",
     "yearly_cost":"$1290",
     "yearly_product_id":"749357",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   },
   {
     "kind":"growth",
@@ -69,6 +76,7 @@
     "monthly_product_id":"749358",
     "yearly_cost":"$1690",
     "yearly_product_id":"749359",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   }
 ]
diff --git a/priv/sandbox_plans.json b/priv/sandbox_plans.json
index 6ff6096e1..483bf2dea 100644
--- a/priv/sandbox_plans.json
+++ b/priv/sandbox_plans.json
@@ -6,7 +6,8 @@
     "monthly_product_id":"63842",
     "yearly_cost":"$90",
     "yearly_product_id":"63859",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -15,7 +16,8 @@
     "monthly_product_id":"63843",
     "yearly_cost":"$190",
     "yearly_product_id":"63860",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -24,7 +26,8 @@
     "monthly_product_id":"63844",
     "yearly_cost":"$290",
     "yearly_product_id":"63861",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -33,7 +36,8 @@
     "monthly_product_id":"63845",
     "yearly_cost":"$490",
     "yearly_product_id":"63862",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -42,7 +46,8 @@
     "monthly_product_id":"63846",
     "yearly_cost":"$690",
     "yearly_product_id":"63863",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -51,7 +56,8 @@
     "monthly_product_id":"63847",
     "yearly_cost":"$890",
     "yearly_product_id":"63864",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -60,7 +66,8 @@
     "monthly_product_id":"63848",
     "yearly_cost":"$1290",
     "yearly_product_id":"63865",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"growth",
@@ -69,7 +76,8 @@
     "monthly_product_id":"63849",
     "yearly_cost":"$1690",
     "yearly_product_id":"63866",
-    "site_limit":10
+    "site_limit":10,
+    "team_member_limit":5
   },
   {
     "kind":"business",
@@ -78,7 +86,8 @@
     "monthly_product_id":"63850",
     "yearly_cost":"$100",
     "yearly_product_id":"63867",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -87,7 +96,8 @@
     "monthly_product_id":"63851",
     "yearly_cost":"$200",
     "yearly_product_id":"63868",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -96,7 +106,8 @@
     "monthly_product_id":"63852",
     "yearly_cost":"$300",
     "yearly_product_id":"63869",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -105,7 +116,8 @@
     "monthly_product_id":"63853",
     "yearly_cost":"$500",
     "yearly_product_id":"63870",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -114,7 +126,8 @@
     "monthly_product_id":"63854",
     "yearly_cost":"$700",
     "yearly_product_id":"63871",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -123,7 +136,8 @@
     "monthly_product_id":"63855",
     "yearly_cost":"$900",
     "yearly_product_id":"63872",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -132,7 +146,8 @@
     "monthly_product_id":"63856",
     "yearly_cost":"$1300",
     "yearly_product_id":"63873",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   },
   {
     "kind":"business",
@@ -141,6 +156,7 @@
     "monthly_product_id":"63857",
     "yearly_cost":"$1700",
     "yearly_product_id":"63874",
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":50
   }
 ]
diff --git a/priv/unlisted_plans_v1.json b/priv/unlisted_plans_v1.json
index e8909e8d1..75e2cf9da 100644
--- a/priv/unlisted_plans_v1.json
+++ b/priv/unlisted_plans_v1.json
@@ -6,6 +6,7 @@
     "yearly_cost":"$4800",
     "monthly_product_id":null,
     "monthly_cost":null,
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   }
 ]
diff --git a/priv/unlisted_plans_v2.json b/priv/unlisted_plans_v2.json
index 8d825c6a5..9c4e9d477 100644
--- a/priv/unlisted_plans_v2.json
+++ b/priv/unlisted_plans_v2.json
@@ -6,6 +6,7 @@
     "monthly_cost":"$250",
     "yearly_product_id":null,
     "yearly_cost":null,
-    "site_limit":50
+    "site_limit":50,
+    "team_member_limit":"unlimited"
   }
 ]
diff --git a/test/plausible/billing/quota_test.exs b/test/plausible/billing/quota_test.exs
index 89967bfdf..6a883a601 100644
--- a/test/plausible/billing/quota_test.exs
+++ b/test/plausible/billing/quota_test.exs
@@ -41,9 +41,6 @@ defmodule Plausible.Billing.QuotaTest do
     test "returns 50 when user in on trial" do
       user = insert(:user, trial_expiry_date: Timex.shift(Timex.now(), days: 7))
       assert 50 == Quota.site_limit(user)
-
-      user = insert(:user, trial_expiry_date: Timex.shift(Timex.now(), days: -7))
-      assert 50 == Quota.site_limit(user)
     end
 
     test "returns the subscription limit for enterprise users who have not paid yet" do
@@ -193,4 +190,155 @@ defmodule Plausible.Billing.QuotaTest do
       assert Quota.monthly_pageview_usage(user) == 0
     end
   end
+
+  describe "team_member_usage/1" do
+    test "returns the number of members in all of the sites the user owns" do
+      me = insert(:user)
+
+      _site_i_own_1 =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :owner),
+            build(:site_membership, user: build(:user), role: :viewer)
+          ]
+        )
+
+      _site_i_own_2 =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :owner),
+            build(:site_membership, user: build(:user), role: :admin),
+            build(:site_membership, user: build(:user), role: :viewer)
+          ]
+        )
+
+      _site_i_own_3 =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :owner)
+          ]
+        )
+
+      _site_i_have_access =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :viewer),
+            build(:site_membership, user: build(:user), role: :viewer),
+            build(:site_membership, user: build(:user), role: :viewer),
+            build(:site_membership, user: build(:user), role: :viewer)
+          ]
+        )
+
+      assert Quota.team_member_usage(me) == 3
+    end
+
+    test "counts the same email address as one team member" do
+      me = insert(:user)
+      joe = insert(:user, email: "joe@plausible.test")
+
+      _site_i_own_1 =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :owner),
+            build(:site_membership, user: joe, role: :viewer)
+          ]
+        )
+
+      _site_i_own_2 =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :owner),
+            build(:site_membership, user: build(:user), role: :admin),
+            build(:site_membership, user: joe, role: :viewer)
+          ]
+        )
+
+      site_i_own_3 = insert(:site, memberships: [build(:site_membership, user: me, role: :owner)])
+
+      insert(:invitation, site: site_i_own_3, inviter: me, email: "joe@plausible.test")
+
+      assert Quota.team_member_usage(me) == 2
+    end
+
+    test "counts pending invitations as team members" do
+      me = insert(:user)
+      member = insert(:user)
+
+      site_i_own =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: me, role: :owner),
+            build(:site_membership, user: member, role: :admin)
+          ]
+        )
+
+      site_i_have_access =
+        insert(:site, memberships: [build(:site_membership, user: me, role: :admin)])
+
+      insert(:invitation, site: site_i_own, inviter: me)
+      insert(:invitation, site: site_i_own, inviter: member)
+      insert(:invitation, site: site_i_have_access, inviter: me)
+
+      assert Quota.team_member_usage(me) == 3
+    end
+
+    test "returns zero when user does not have any site" do
+      me = insert(:user)
+      assert Quota.team_member_usage(me) == 0
+    end
+
+    test "does not count email report recipients as team members" do
+      me = insert(:user)
+      site = insert(:site, memberships: [build(:site_membership, user: me, role: :owner)])
+
+      insert(:weekly_report,
+        site: site,
+        recipients: ["adam@plausible.test", "vini@plausible.test"]
+      )
+
+      assert Quota.team_member_usage(me) == 0
+    end
+  end
+
+  describe "team_member_limit/1" do
+    test "returns unlimited when user is on an old plan" do
+      user_on_v1 = insert(:user, subscription: build(:subscription, paddle_plan_id: @v1_plan_id))
+      user_on_v2 = insert(:user, subscription: build(:subscription, paddle_plan_id: @v2_plan_id))
+      user_on_v3 = insert(:user, subscription: build(:subscription, paddle_plan_id: @v3_plan_id))
+
+      assert :unlimited == Quota.team_member_limit(user_on_v1)
+      assert :unlimited == Quota.team_member_limit(user_on_v2)
+      assert :unlimited == Quota.team_member_limit(user_on_v3)
+    end
+
+    test "returns unlimited when user is on free_10k plan" do
+      user = insert(:user, subscription: build(:subscription, paddle_plan_id: "free_10k"))
+      assert :unlimited == Quota.team_member_limit(user)
+    end
+
+    test "returns unlimited when user is on an enterprise plan" do
+      user = insert(:user)
+      enterprise_plan = insert(:enterprise_plan, user_id: user.id)
+
+      _subscription =
+        insert(:subscription, user_id: user.id, paddle_plan_id: enterprise_plan.paddle_plan_id)
+
+      assert :unlimited == Quota.team_member_limit(user)
+    end
+
+    test "returns 5 when user in on trial" do
+      user = insert(:user, trial_expiry_date: Timex.shift(Timex.now(), days: 7))
+      assert 5 == Quota.team_member_limit(user)
+    end
+
+    test "is unlimited for enterprise customers" do
+      user =
+        insert(:user,
+          enterprise_plan: build(:enterprise_plan, paddle_plan_id: "123321"),
+          subscription: build(:subscription, paddle_plan_id: "123321")
+        )
+
+      assert :unlimited == Quota.team_member_limit(user)
+    end
+  end
 end
diff --git a/test/plausible/site/sites_test.exs b/test/plausible/site/sites_test.exs
index 2f69d5501..42c941b64 100644
--- a/test/plausible/site/sites_test.exs
+++ b/test/plausible/site/sites_test.exs
@@ -1,5 +1,6 @@
 defmodule Plausible.SitesTest do
   use Plausible.DataCase
+  use Bamboo.Test
 
   alias Plausible.Sites
 
@@ -67,4 +68,79 @@ defmodule Plausible.SitesTest do
       assert Sites.has_stats?(site)
     end
   end
+
+  describe "invite/4" do
+    test "creates an invitation" do
+      inviter = insert(:user)
+      invitee = insert(:user)
+      site = insert(:site, memberships: [build(:site_membership, user: inviter, role: :owner)])
+
+      assert {:ok, %Plausible.Auth.Invitation{}} =
+               Sites.invite(site, inviter, invitee.email, :viewer)
+    end
+
+    test "returns validation errors" do
+      inviter = insert(:user)
+      invitee = insert(:user)
+      site = insert(:site, memberships: [build(:site_membership, user: inviter, role: :owner)])
+
+      assert {:error, changeset} = Sites.invite(site, inviter, invitee.email, :invalid_role)
+      assert {"is invalid", _} = changeset.errors[:role]
+    end
+
+    test "returns error when user is already a member" do
+      inviter = insert(:user)
+      invitee = insert(:user)
+
+      site =
+        insert(:site,
+          memberships: [
+            build(:site_membership, user: inviter, role: :owner),
+            build(:site_membership, user: invitee, role: :viewer)
+          ]
+        )
+
+      assert {:error, :already_a_member} = Sites.invite(site, inviter, invitee.email, :viewer)
+      assert {:error, :already_a_member} = Sites.invite(site, inviter, inviter.email, :viewer)
+    end
+
+    test "sends invitation email for existing users" do
+      [inviter, invitee] = insert_list(2, :user)
+      site = insert(:site, memberships: [build(:site_membership, user: inviter, role: :owner)])
+
+      assert {:ok, %Plausible.Auth.Invitation{}} =
+               Sites.invite(site, inviter, invitee.email, :viewer)
+
+      assert_email_delivered_with(
+        to: [nil: invitee.email],
+        subject: "[Plausible Analytics] You've been invited to #{site.domain}"
+      )
+    end
+
+    test "sends invitation email for new users" do
+      inviter = insert(:user)
+      site = insert(:site, memberships: [build(:site_membership, user: inviter, role: :owner)])
+
+      assert {:ok, %Plausible.Auth.Invitation{}} =
+               Sites.invite(site, inviter, "vini@plausible.test", :viewer)
+
+      assert_email_delivered_with(
+        to: [nil: "vini@plausible.test"],
+        subject: "[Plausible Analytics] You've been invited to #{site.domain}"
+      )
+    end
+
+    test "returns error when owner is over their team member limit" do
+      [owner, inviter, invitee] = insert_list(3, :user)
+
+      memberships =
+        [
+          build(:site_membership, user: owner, role: :owner),
+          build(:site_membership, user: inviter, role: :admin)
+        ] ++ build_list(4, :site_membership)
+
+      site = insert(:site, memberships: memberships)
+      assert {:error, {:over_limit, 5}} = Sites.invite(site, inviter, invitee.email, :viewer)
+    end
+  end
 end
diff --git a/test/plausible_web/controllers/site/membership_controller_test.exs b/test/plausible_web/controllers/site/membership_controller_test.exs
index f87625cb4..8afbefc6b 100644
--- a/test/plausible_web/controllers/site/membership_controller_test.exs
+++ b/test/plausible_web/controllers/site/membership_controller_test.exs
@@ -31,6 +31,22 @@ defmodule PlausibleWeb.Site.MembershipControllerTest do
       assert redirected_to(conn) == "/#{site.domain}/settings/people"
     end
 
+    test "fails to create invitation when is over limit", %{conn: conn, user: user} do
+      memberships =
+        [build(:site_membership, user: user, role: :owner)] ++ build_list(5, :site_membership)
+
+      site = insert(:site, memberships: memberships)
+
+      conn =
+        post(conn, "/sites/#{site.domain}/memberships/invite", %{
+          email: "john.doe@example.com",
+          role: "admin"
+        })
+
+      assert html_response(conn, 200) =~
+               "Your account is limited to 5 team members. You can upgrade your plan to increase this limit."
+    end
+
     test "fails to create invitation with insufficient permissions", %{conn: conn, user: user} do
       site = insert(:site, memberships: [build(:site_membership, user: user, role: :viewer)])
 
@@ -95,7 +111,13 @@ defmodule PlausibleWeb.Site.MembershipControllerTest do
 
     test "renders form with error if the invitee is already a member", %{conn: conn, user: user} do
       second_member = insert(:user)
-      site = insert(:site, members: [user, second_member])
+
+      memberships = [
+        build(:site_membership, user: user, role: :owner),
+        build(:site_membership, user: second_member)
+      ]
+
+      site = insert(:site, memberships: memberships)
 
       conn =
         post(conn, "/sites/#{site.domain}/memberships/invite", %{
diff --git a/test/support/factory.ex b/test/support/factory.ex
index fc74a57bd..591a69918 100644
--- a/test/support/factory.ex
+++ b/test/support/factory.ex
@@ -32,7 +32,10 @@ defmodule Plausible.Factory do
   end
 
   def site_membership_factory do
-    %Plausible.Site.Membership{}
+    %Plausible.Site.Membership{
+      user: build(:user),
+      role: :viewer
+    }
   end
 
   def ch_session_factory do