diff --git a/Cargo.lock b/Cargo.lock
index 59fa45c41..92d64f745 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4514,6 +4514,7 @@ dependencies = [
  "promise",
  "structopt",
  "umask",
+ "wezterm-gui-subcommands",
  "wezterm-mux-server-impl",
  "winapi 0.3.9",
 ]
diff --git a/config/src/lib.rs b/config/src/lib.rs
index 58fd499b5..e1a8ef064 100644
--- a/config/src/lib.rs
+++ b/config/src/lib.rs
@@ -60,6 +60,7 @@ lazy_static! {
     pub static ref RUNTIME_DIR: PathBuf = compute_runtime_dir().unwrap();
     static ref CONFIG: Configuration = Configuration::new();
     static ref CONFIG_FILE_OVERRIDE: Mutex<Option<PathBuf>> = Mutex::new(None);
+    static ref CONFIG_OVERRIDES: Mutex<Vec<(String, String)>> = Mutex::new(vec![]);
     static ref MAKE_LUA: Mutex<Option<LuaFactory>> = Mutex::new(Some(lua::make_lua_context));
     static ref SHOW_ERROR: Mutex<Option<ErrorCallback>> =
         Mutex::new(Some(|e| log::error!("{}", e)));
@@ -206,6 +207,47 @@ fn make_lua_context(path: &Path) -> anyhow::Result<Lua> {
     }
 }
 
+fn default_config_with_overrides_applied() -> anyhow::Result<Config> {
+    // Cause the default config to be re-evaluated with the overrides applied
+    let lua = make_lua_context(Path::new("override"))?;
+    let table = mlua::Value::Table(lua.create_table()?);
+    let config = Config::apply_overrides_to(&lua, table)?;
+
+    let cfg: Config = luahelper::from_lua_value(config)
+        .context("Error converting lua value from overrides to Config struct")?;
+    // Compute but discard the key bindings here so that we raise any
+    // problems earlier than we use them.
+    let _ = cfg.key_bindings();
+
+    Ok(cfg)
+}
+
+pub fn common_init(
+    config_file: Option<&OsString>,
+    overrides: &[(String, String)],
+    skip_config: bool,
+) {
+    if let Some(config_file) = config_file {
+        set_config_file_override(Path::new(config_file));
+    }
+    set_config_overrides(overrides);
+    if !skip_config {
+        reload();
+    } else if !overrides.is_empty() {
+        match default_config_with_overrides_applied() {
+            Ok(cfg) => CONFIG.use_this_config(cfg),
+            Err(err) => {
+                log::error!(
+                    "Error while applying command line \
+                     configuration overrides:\n{:#}",
+                    err
+                );
+                std::process::exit(1);
+            }
+        }
+    }
+}
+
 pub fn assign_error_callback(cb: ErrorCallback) {
     let mut factory = SHOW_ERROR.lock().unwrap();
     factory.replace(cb);
@@ -247,9 +289,12 @@ pub fn set_config_file_override(path: &Path) {
         .replace(path.to_path_buf());
 }
 
+pub fn set_config_overrides(items: &[(String, String)]) {
+    *CONFIG_OVERRIDES.lock().unwrap() = items.to_vec();
+}
+
 /// Discard the current configuration and replace it with
 /// the default configuration
-#[allow(dead_code)]
 pub fn use_default_configuration() {
     CONFIG.use_defaults();
 }
@@ -396,6 +441,12 @@ impl ConfigInner {
         self.generation += 1;
     }
 
+    fn use_this_config(&mut self, cfg: Config) {
+        self.config = Arc::new(cfg);
+        self.error.take();
+        self.generation += 1;
+    }
+
     fn use_test(&mut self) {
         FontLocatorSelection::ConfigDirsOnly.set_default();
         let mut config = Config::default_config();
@@ -435,6 +486,11 @@ impl Configuration {
         inner.use_defaults();
     }
 
+    fn use_this_config(&self, cfg: Config) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.use_this_config(cfg);
+    }
+
     /// Use a config that doesn't depend on the user's
     /// environment and is suitable for unit testing
     pub fn use_test(&self) {
@@ -1135,6 +1191,7 @@ impl Config {
                     .set_name(p.to_string_lossy().as_bytes())?
                     .eval_async(),
             )?;
+            let config = Self::apply_overrides_to(&lua, config)?;
             cfg = luahelper::from_lua_value(config).with_context(|| {
                 format!(
                     "Error converting lua value returned by script {} to Config struct",
@@ -1164,6 +1221,29 @@ impl Config {
         })
     }
 
+    fn apply_overrides_to<'l>(
+        lua: &'l mlua::Lua,
+        mut config: mlua::Value<'l>,
+    ) -> anyhow::Result<mlua::Value<'l>> {
+        let overrides = CONFIG_OVERRIDES.lock().unwrap();
+        for (key, value) in &*overrides {
+            let code = format!(
+                r#"
+                local wezterm = require 'wezterm';
+                config.{} = {};
+                return config;
+                "#,
+                key, value
+            );
+            let chunk = lua.load(&code);
+            let chunk = chunk.set_name(&format!("--config {}={}", key, value))?;
+            lua.globals().set("config", config.clone())?;
+            log::debug!("Apply {}={} to config", key, value);
+            config = chunk.eval()?;
+        }
+        Ok(config)
+    }
+
     pub fn default_config() -> Self {
         Self::default().compute_extra_defaults(None)
     }
diff --git a/docs/changelog.md b/docs/changelog.md
index 2ed111fc3..74d4371d0 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -33,6 +33,7 @@ brief notes about them may accumulate here.
 * Windows: Fixed [ToggleFullScreen](config/lua/keyassignment/ToggleFullScreen.md) so that it once again toggles between full screen and normal placement. [#177](https://github.com/wez/wezterm/issues/177)
 * New: [exit_behavior](config/lua/config/exit_behavior.md) config option to keep panes open after the program has completed. [#499](https://github.com/wez/wezterm/issues/499)
 * Closing the configuration error window no longer requires confirmation
+* New: added `--config name=value` options to `wezterm`, `wezterm-gui` and `wezterm-mux-server`
 
 ### 20210203-095643-70a364eb
 
diff --git a/wezterm-gui-subcommands/src/lib.rs b/wezterm-gui-subcommands/src/lib.rs
index 64915747a..fc7abab04 100644
--- a/wezterm-gui-subcommands/src/lib.rs
+++ b/wezterm-gui-subcommands/src/lib.rs
@@ -5,6 +5,24 @@ use config::{FrontEndSelection, SshParameters};
 use std::ffi::OsString;
 use structopt::StructOpt;
 
+/// Helper for parsing config overrides
+pub fn name_equals_value(arg: &str) -> Result<(String, String), String> {
+    if let Some(eq) = arg.find('=') {
+        let (left, right) = arg.split_at(eq);
+        let left = left.trim();
+        let right = right[1..].trim();
+        if left.is_empty() || right.is_empty() {
+            return Err(format!(
+                "Got empty name/value `{}`; expected name=value",
+                arg
+            ));
+        }
+        Ok((left.to_string(), right.to_string()))
+    } else {
+        Err(format!("Expected name=value, but got {}", arg))
+    }
+}
+
 #[derive(Debug, StructOpt, Default, Clone)]
 pub struct StartCommand {
     #[structopt(
diff --git a/wezterm-gui/src/main.rs b/wezterm-gui/src/main.rs
index b890abb30..2ce40faeb 100644
--- a/wezterm-gui/src/main.rs
+++ b/wezterm-gui/src/main.rs
@@ -43,6 +43,14 @@ struct Opt {
     )]
     config_file: Option<OsString>,
 
+    /// Override specific configuration values
+    #[structopt(
+        long = "config",
+        name = "name=value",
+        parse(try_from_str = name_equals_value),
+        number_of_values = 1)]
+    config_override: Vec<(String, String)>,
+
     #[structopt(subcommand)]
     cmd: Option<SubCommand>,
 }
@@ -446,12 +454,11 @@ fn run() -> anyhow::Result<()> {
     let _saver = umask::UmaskSaver::new();
 
     let opts = Opt::from_args();
-    if let Some(config_file) = opts.config_file.as_ref() {
-        config::set_config_file_override(std::path::Path::new(config_file));
-    }
-    if !opts.skip_config {
-        config::reload();
-    }
+    config::common_init(
+        opts.config_file.as_ref(),
+        &opts.config_override,
+        opts.skip_config,
+    );
     let config = config::configuration();
     window::configuration::set_configuration(crate::window_config::ConfigBridge);
 
diff --git a/wezterm-mux-server/Cargo.toml b/wezterm-mux-server/Cargo.toml
index d2f9d5445..af68db2dd 100644
--- a/wezterm-mux-server/Cargo.toml
+++ b/wezterm-mux-server/Cargo.toml
@@ -20,6 +20,7 @@ promise = { path = "../promise" }
 structopt = "0.3"
 umask = { path = "../umask" }
 wezterm-mux-server-impl = { path = "../wezterm-mux-server-impl" }
+wezterm-gui-subcommands = { path = "../wezterm-gui-subcommands" }
 
 [target."cfg(windows)".dependencies]
 winapi = { version = "0.3", features = [ "winuser" ]}
diff --git a/wezterm-mux-server/src/main.rs b/wezterm-mux-server/src/main.rs
index e866168db..8ea58e96d 100644
--- a/wezterm-mux-server/src/main.rs
+++ b/wezterm-mux-server/src/main.rs
@@ -9,6 +9,7 @@ use std::rc::Rc;
 use std::sync::Arc;
 use std::thread;
 use structopt::*;
+use wezterm_gui_subcommands::*;
 
 mod daemonize;
 
@@ -32,6 +33,14 @@ struct Opt {
     )]
     config_file: Option<OsString>,
 
+    /// Override specific configuration values
+    #[structopt(
+        long = "config",
+        name = "name=value",
+        parse(try_from_str = name_equals_value),
+        number_of_values = 1)]
+    config_override: Vec<(String, String)>,
+
     /// Detach from the foreground and become a background process
     #[structopt(long = "daemonize")]
     daemonize: bool,
@@ -63,12 +72,11 @@ fn run() -> anyhow::Result<()> {
     let _saver = umask::UmaskSaver::new();
 
     let opts = Opt::from_args();
-    if let Some(config_file) = opts.config_file.as_ref() {
-        config::set_config_file_override(std::path::Path::new(config_file));
-    }
-    if !opts.skip_config {
-        config::reload();
-    }
+    config::common_init(
+        opts.config_file.as_ref(),
+        &opts.config_override,
+        opts.skip_config,
+    );
 
     #[cfg(unix)]
     {
diff --git a/wezterm/src/main.rs b/wezterm/src/main.rs
index d6bc86dbe..733d617ec 100644
--- a/wezterm/src/main.rs
+++ b/wezterm/src/main.rs
@@ -38,6 +38,14 @@ struct Opt {
     )]
     config_file: Option<OsString>,
 
+    /// Override specific configuration values
+    #[structopt(
+        long = "config",
+        name = "name=value",
+        parse(try_from_str = name_equals_value),
+        number_of_values = 1)]
+    config_override: Vec<(String, String)>,
+
     #[structopt(subcommand)]
     cmd: Option<SubCommand>,
 }
@@ -236,12 +244,11 @@ fn run() -> anyhow::Result<()> {
     let saver = UmaskSaver::new();
 
     let opts = Opt::from_args();
-    if let Some(config_file) = opts.config_file.as_ref() {
-        config::set_config_file_override(std::path::Path::new(config_file));
-    }
-    if !opts.skip_config {
-        config::reload();
-    }
+    config::common_init(
+        opts.config_file.as_ref(),
+        &opts.config_override,
+        opts.skip_config,
+    );
     let config = config::configuration();
 
     match opts