diff --git a/src/Internal/Api/Invite/Api.elm b/src/Internal/Api/Invite/Api.elm
new file mode 100644
index 0000000..2d5e2e2
--- /dev/null
+++ b/src/Internal/Api/Invite/Api.elm
@@ -0,0 +1,137 @@
+module Internal.Api.Invite.Api exposing (InviteInput, Phantom, invite)
+
+{-|
+
+
+# Invite
+
+This API invites a user to participate in a particular room. They do not start
+participating in the room until they actually join the room.
+
+Only users currently in a particular room can invite other users to join that
+room.
+
+If the user was invited to the room, the homeserver will append a m.room.member
+event to the room.
+
+@docs InviteInput, Phantom, invite
+
+-}
+
+import Internal.Api.Api as A
+import Internal.Api.Request as R
+import Internal.Config.Log exposing (log)
+import Internal.Tools.Json as Json
+import Internal.Values.Room as Room
+import Internal.Values.User as User exposing (User)
+import Internal.Values.Vault as V
+
+
+{-| Invite a user to a room.
+-}
+invite : InviteInput -> A.TaskChain (Phantom ph1) (Phantom ph1)
+invite =
+    A.startWithVersion "r0.0.0" inviteV1
+        |> A.sameForVersion "r0.0.1"
+        |> A.sameForVersion "r0.1.0"
+        |> A.sameForVersion "r0.2.0"
+        |> A.sameForVersion "r0.3.0"
+        |> A.sameForVersion "r0.4.0"
+        |> A.sameForVersion "r0.5.0"
+        |> A.sameForVersion "r0.6.0"
+        |> A.sameForVersion "r0.6.1"
+        |> A.forVersion "v1.1" inviteV2
+        |> A.sameForVersion "v1.2"
+        |> A.sameForVersion "v1.3"
+        |> A.sameForVersion "v1.4"
+        |> A.sameForVersion "v1.5"
+        |> A.sameForVersion "v1.6"
+        |> A.sameForVersion "v1.7"
+        |> A.sameForVersion "v1.8"
+        |> A.sameForVersion "v1.9"
+        |> A.sameForVersion "v1.10"
+        |> A.versionChain
+
+
+{-| Context needed for inviting a user.
+-}
+type alias Phantom a =
+    { a | accessToken : (), versions : () }
+
+
+type alias PhantomV1 a =
+    { a | accessToken : () }
+
+
+{-| Input for inviting a user.
+-}
+type alias InviteInput =
+    { reason : Maybe String, roomId : String, user : User }
+
+
+type alias InviteInputV1 a =
+    { a | roomId : String, user : User }
+
+
+type alias InviteInputV2 a =
+    { a | roomId : String, user : User, reason : Maybe String }
+
+
+inviteV1 : InviteInputV1 a -> A.TaskChain (PhantomV1 ph1) (PhantomV1 ph1)
+inviteV1 { roomId, user } =
+    A.request
+        { attributes =
+            [ R.accessToken
+            , R.bodyString "user_id" (User.toString user)
+            , R.onStatusCode 400 "M_UNKNOWN"
+            , R.onStatusCode 403 "M_FORBIDDEN"
+            , R.onStatusCode 429 "M_LIMIT_EXCEEDED"
+            ]
+        , coder = Json.value
+        , contextChange = always identity
+        , method = "POST"
+        , path = [ "_matrix", "client", "r0", "rooms", roomId, "invite" ]
+        , toUpdate =
+            always
+                ( V.MapRoom roomId (Room.Invite user)
+                , String.concat
+                    -- TODO: Move to Internal.Config.Text
+                    [ "Invited user "
+                    , User.toString user
+                    , " to room "
+                    , roomId
+                    ]
+                    |> log.debug
+                    |> List.singleton
+                )
+        }
+
+
+inviteV2 : InviteInputV2 a -> A.TaskChain (PhantomV1 ph1) (PhantomV1 ph1)
+inviteV2 { reason, roomId, user } =
+    A.request
+        { attributes =
+            [ R.bodyOpString "reason" reason
+            , R.bodyString "user_id" (User.toString user)
+            , R.onStatusCode 400 "M_UNKNOWN"
+            , R.onStatusCode 403 "M_FORBIDDEN"
+            , R.onStatusCode 429 "M_LIMIT_EXCEEDED"
+            ]
+        , coder = Json.value
+        , contextChange = always identity
+        , method = "POST"
+        , path = [ "_matrix", "client", "v3", "rooms", roomId, "invite" ]
+        , toUpdate =
+            always
+                ( V.MapRoom roomId (Room.Invite user)
+                , String.concat
+                    -- TODO: Move to Internal.Config.Text
+                    [ "Invited user "
+                    , User.toString user
+                    , " to room "
+                    , roomId
+                    ]
+                    |> log.debug
+                    |> List.singleton
+                )
+        }