diff --git a/src/js.rs b/src/js.rs
index 6ece49ac3..c96f0ed16 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -360,6 +360,13 @@ extern {
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/clz32
     #[wasm_bindgen(static_method_of = Math)]
     pub fn clz32(x: i32) -> Number;
+
+    /// The Math.floor() function returns the largest integer less than or
+    /// equal to a given number.
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor
+    #[wasm_bindgen(static_method_of = Math)]
+    pub fn floor(x: f32) -> Number;
 }
 
 // Number.
diff --git a/tests/all/js_globals/Math.rs b/tests/all/js_globals/Math.rs
index 1fbf95028..df3038f4d 100644
--- a/tests/all/js_globals/Math.rs
+++ b/tests/all/js_globals/Math.rs
@@ -292,3 +292,30 @@ fn clz32() {
         "#)
         .test()
 }
+
+#[test]
+fn floor() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn floor(x: f32) -> js::Number {
+                js::Math::floor(x)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                assert.equal(wasm.floor(5.95), 5);
+                assert.equal(wasm.floor(-5.05), -6);
+            }
+        "#)
+        .test()
+}