diff --git a/ruma-client/src/http_client.rs b/ruma-client/src/http_client.rs
index 030445f3..c2ca2a52 100644
--- a/ruma-client/src/http_client.rs
+++ b/ruma-client/src/http_client.rs
@@ -6,8 +6,9 @@ use std::{future::Future, pin::Pin};
 use async_trait::async_trait;
 use bytes::BufMut;
 use ruma_api::{OutgoingRequest, SendAccessToken};
+use ruma_identifiers::UserId;
 
-use crate::{ResponseError, ResponseResult};
+use crate::{add_user_id_to_query, ResponseError, ResponseResult};
 
 #[cfg(feature = "hyper")]
 mod hyper;
@@ -90,6 +91,29 @@ pub trait HttpClientExt: HttpClient {
             customize,
         ))
     }
+
+    /// Turn a strongly-typed matrix request into an `http::Request`, add a `user_id` query
+    /// parameter to it and send it to get back a strongly-typed response.
+    ///
+    /// This method is meant to be used by application services when interacting with the
+    /// client-server API.
+    fn send_request_as<'a, R: OutgoingRequest + 'a>(
+        &'a self,
+        homeserver_url: &str,
+        access_token: SendAccessToken<'_>,
+        user_id: &'a UserId,
+        request: R,
+    ) -> Pin<Box<dyn Future<Output = ResponseResult<Self, R>> + 'a>>
+    where
+        <R as OutgoingRequest>::EndpointError: Send,
+    {
+        self.send_customized_request(
+            homeserver_url,
+            access_token,
+            request,
+            add_user_id_to_query::<Self, R>(user_id),
+        )
+    }
 }
 
 #[async_trait]
diff --git a/ruma-client/src/lib.rs b/ruma-client/src/lib.rs
index eef15488..3f69540d 100644
--- a/ruma-client/src/lib.rs
+++ b/ruma-client/src/lib.rs
@@ -79,6 +79,7 @@ use std::{
 };
 
 use ruma_api::{OutgoingRequest, SendAccessToken};
+use ruma_identifiers::UserId;
 
 // "Undo" rename from `Cargo.toml` that only serves to make `hyper-rustls` available as a Cargo
 // feature name.
@@ -190,6 +191,21 @@ impl<C: HttpClient> Client<C> {
         )
         .await
     }
+
+    /// Makes a request to a Matrix API endpoint as a virtual user.
+    ///
+    /// This method is meant to be used by application services when interacting with the
+    /// client-server API.
+    pub async fn send_request_as<R: OutgoingRequest>(
+        &self,
+        user_id: &UserId,
+        request: R,
+    ) -> ResponseResult<C, R>
+    where
+        <R as OutgoingRequest>::EndpointError: Send,
+    {
+        self.send_customized_request(request, add_user_id_to_query::<C, R>(user_id)).await
+    }
 }
 
 fn send_customized_request<'a, C, R, F>(
@@ -218,3 +234,25 @@ where
         Ok(ruma_api::IncomingResponse::try_from_http_response(http_res)?)
     }
 }
+
+fn add_user_id_to_query<C: HttpClient + ?Sized, R: OutgoingRequest>(
+    user_id: &UserId,
+) -> impl FnOnce(&mut http::Request<C::RequestBody>) -> Result<(), ResponseError<C, R>> + '_ {
+    use assign::assign;
+    use http::uri::Uri;
+    use ruma_serde::urlencoded;
+
+    move |http_request| {
+        let extra_params = urlencoded::to_string(&[("user_id", user_id)]).unwrap();
+        let uri = http_request.uri_mut();
+        let new_path_and_query = match uri.query() {
+            Some(params) => format!("{}?{}&{}", uri.path(), params, extra_params),
+            None => format!("{}?{}", uri.path(), extra_params),
+        };
+        *uri = Uri::from_parts(assign!(uri.clone().into_parts(), {
+            path_and_query: Some(new_path_and_query.parse()?),
+        }))?;
+
+        Ok(())
+    }
+}