diff --git a/crates/ruma-identity-service-api/CHANGELOG.md b/crates/ruma-identity-service-api/CHANGELOG.md
index 0d00ab24..ae95294b 100644
--- a/crates/ruma-identity-service-api/CHANGELOG.md
+++ b/crates/ruma-identity-service-api/CHANGELOG.md
@@ -8,7 +8,8 @@ Improvements:
   association::{
       check_3pid_validity::v2,
       bind_3pid::v2,
-  }
+  },
+  invitation::sign_invitation_ed25519::v2
   ```
 
 # 0.1.0
diff --git a/crates/ruma-identity-service-api/src/invitation.rs b/crates/ruma-identity-service-api/src/invitation.rs
new file mode 100644
index 00000000..db034d65
--- /dev/null
+++ b/crates/ruma-identity-service-api/src/invitation.rs
@@ -0,0 +1,2 @@
+//! Endpoints for ephemeral invitation signing.
+pub mod sign_invitation_ed25519;
diff --git a/crates/ruma-identity-service-api/src/invitation/sign_invitation_ed25519.rs b/crates/ruma-identity-service-api/src/invitation/sign_invitation_ed25519.rs
new file mode 100644
index 00000000..53a64ac1
--- /dev/null
+++ b/crates/ruma-identity-service-api/src/invitation/sign_invitation_ed25519.rs
@@ -0,0 +1,2 @@
+//! Endpoint to sign invitation details.
+pub mod v2;
diff --git a/crates/ruma-identity-service-api/src/invitation/sign_invitation_ed25519/v2.rs b/crates/ruma-identity-service-api/src/invitation/sign_invitation_ed25519/v2.rs
new file mode 100644
index 00000000..3440a9af
--- /dev/null
+++ b/crates/ruma-identity-service-api/src/invitation/sign_invitation_ed25519/v2.rs
@@ -0,0 +1,54 @@
+//![POST /_matrix/identity/v2/sign-ed25519](https://matrix.org/docs/spec/identity_service/r0.3.0#post-matrix-identity-v2-sign-ed25519)
+
+use ruma_api::ruma_api;
+use ruma_identifiers::{ServerSignatures, UserId};
+
+ruma_api! {
+    metadata: {
+        description: "Sign invitation details.",
+        method: POST,
+        name: "sign_invitation_ed25519",
+        path: "/_matrix/identity/v2/sign-ed25519",
+        authentication: AccessToken,
+        rate_limited: false,
+    }
+
+    request: {
+        /// The Matrix user ID of the user accepting the invitation.
+        pub mxid: UserId,
+
+        /// The token from the call to store-invite.
+        pub token: &'a str,
+
+        /// The private key, encoded as unpadded base64.
+        pub private_key: &'a str,
+    }
+
+    response: {
+        /// The Matrix user ID of the user accepting the invitation.
+        pub mxid: UserId,
+
+        /// The Matrix user ID of the user who sent the invitation.
+        pub sender: UserId,
+
+        /// The signature of the mxid, sender and token.
+        pub signatures: ServerSignatures,
+
+        /// The token for the invitation.
+        pub token: String,
+    }
+}
+
+impl<'a> Request<'a> {
+    /// Creates a `Request` with the given Matrix user ID, token and private_key.
+    pub fn new(mxid: UserId, token: &'a str, private_key: &'a str) -> Self {
+        Self { mxid, token, private_key }
+    }
+}
+
+impl Response {
+    /// Creates a `Response` with the given Matrix user ID, sender user ID, signatures and token.
+    pub fn new(mxid: UserId, sender: UserId, signatures: ServerSignatures, token: String) -> Self {
+        Self { mxid, sender, signatures, token }
+    }
+}
diff --git a/crates/ruma-identity-service-api/src/lib.rs b/crates/ruma-identity-service-api/src/lib.rs
index 462cff69..e6a5178c 100644
--- a/crates/ruma-identity-service-api/src/lib.rs
+++ b/crates/ruma-identity-service-api/src/lib.rs
@@ -9,6 +9,7 @@
 
 pub mod association;
 pub mod authentication;
+pub mod invitation;
 pub mod keys;
 pub mod lookup;
 pub mod status;