diff --git a/crates/ruma-client-api/CHANGELOG.md b/crates/ruma-client-api/CHANGELOG.md
index 1323f5be..6c45faee 100644
--- a/crates/ruma-client-api/CHANGELOG.md
+++ b/crates/ruma-client-api/CHANGELOG.md
@@ -8,6 +8,7 @@ Improvements:
   r0::knock::knock_room
   ```
 * Add unstable support for room knocking.
+* Add unstable support for reasons for leaving rooms
 
 # 0.11.0
 
diff --git a/crates/ruma-client-api/src/r0/membership/leave_room.rs b/crates/ruma-client-api/src/r0/membership/leave_room.rs
index d900df20..f787f2e9 100644
--- a/crates/ruma-client-api/src/r0/membership/leave_room.rs
+++ b/crates/ruma-client-api/src/r0/membership/leave_room.rs
@@ -17,6 +17,12 @@ ruma_api! {
         /// The room to leave.
         #[ruma_api(path)]
         pub room_id: &'a RoomId,
+
+        /// Optional reason to be included as the `reason` on the subsequent membership event.
+        #[cfg(feature = "unstable-pre-spec")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "unstable-pre-spec")))]
+        #[serde(skip_serializing_if = "Option::is_none")]
+        pub reason: Option<&'a str>,
     }
 
     #[derive(Default)]
@@ -28,7 +34,11 @@ ruma_api! {
 impl<'a> Request<'a> {
     /// Creates a new `Request` with the given room id.
     pub fn new(room_id: &'a RoomId) -> Self {
-        Self { room_id }
+        Self {
+            room_id,
+            #[cfg(feature = "unstable-pre-spec")]
+            reason: None,
+        }
     }
 }
 
diff --git a/crates/ruma-events/src/room/member.rs b/crates/ruma-events/src/room/member.rs
index 2f8916e6..af029788 100644
--- a/crates/ruma-events/src/room/member.rs
+++ b/crates/ruma-events/src/room/member.rs
@@ -79,6 +79,12 @@ pub struct MemberEventContent {
     #[serde(rename = "xyz.amorgan.blurhash")]
     #[serde(skip_serializing_if = "Option::is_none")]
     pub blurhash: Option<String>,
+
+    /// The reason for leaving a room.
+    #[cfg(feature = "unstable-pre-spec")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "unstable-pre-spec")))]
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub reason: Option<String>,
 }
 
 impl MemberEventContent {
@@ -92,6 +98,8 @@ impl MemberEventContent {
             third_party_invite: None,
             #[cfg(feature = "unstable-pre-spec")]
             blurhash: None,
+            #[cfg(feature = "unstable-pre-spec")]
+            reason: None,
         }
     }
 }
@@ -241,6 +249,8 @@ fn membership_change(
             third_party_invite: None,
             #[cfg(feature = "unstable-pre-spec")]
             blurhash: None,
+            #[cfg(feature = "unstable-pre-spec")]
+            reason: None,
         }
     };