diff --git a/src/Common/src/System/Net/Http/HttpHandlerDefaults.cs b/src/Common/src/System/Net/Http/HttpHandlerDefaults.cs
index b32f4d7d81d9..9f0f6b72b911 100644
--- a/src/Common/src/System/Net/Http/HttpHandlerDefaults.cs
+++ b/src/Common/src/System/Net/Http/HttpHandlerDefaults.cs
@@ -2,7 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Diagnostics;
+using System.IO;
 using System.Threading;
+using System.Threading.Tasks;
 
 namespace System.Net.Http
 {
diff --git a/src/System.Net.Http/ref/System.Net.Http.cs b/src/System.Net.Http/ref/System.Net.Http.cs
index 8e4860a69790..378f70de73b1 100644
--- a/src/System.Net.Http/ref/System.Net.Http.cs
+++ b/src/System.Net.Http/ref/System.Net.Http.cs
@@ -262,6 +262,7 @@ public SocketsHttpHandler() { }
         public System.Net.IWebProxy Proxy { get { throw null; } set { } }
         public System.TimeSpan ResponseDrainTimeout { get { throw null; } set { } }
         public System.Net.Security.SslClientAuthenticationOptions SslOptions { get { throw null; } set { } }
+        public System.Func<string, int, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<System.IO.Stream>> ConnectCallback {  get { throw null; } set { } }
         public bool UseCookies { get { throw null; } set { } }
         public bool UseProxy { get { throw null; } set { } }
         protected override void Dispose(bool disposing) { }
diff --git a/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs b/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs
index 843882ad6e5c..3a9cce0e2272 100644
--- a/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs
+++ b/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs
@@ -622,11 +622,11 @@ public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, bool doRe
                     case HttpConnectionKind.Http:
                     case HttpConnectionKind.Https:
                     case HttpConnectionKind.ProxyConnect:
-                        stream = await ConnectHelper.ConnectAsync(_host, _port, cancellationToken).ConfigureAwait(false);
+                        stream = await Settings._customConnect(_host, _port, cancellationToken).ConfigureAwait(false);
                         break;
 
                     case HttpConnectionKind.Proxy:
-                        stream = await ConnectHelper.ConnectAsync(_proxyUri.IdnHost, _proxyUri.Port, cancellationToken).ConfigureAwait(false);
+                        stream = await Settings._customConnect(_proxyUri.IdnHost, _proxyUri.Port, cancellationToken).ConfigureAwait(false);
                         break;
 
                     case HttpConnectionKind.ProxyTunnel:
diff --git a/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionSettings.cs b/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionSettings.cs
index f6788731ce8c..c8497196b631 100644
--- a/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionSettings.cs
+++ b/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionSettings.cs
@@ -3,7 +3,11 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
 using System.Net.Security;
+using System.Threading;
+using System.Threading.Tasks;
 
 namespace System.Net.Http
 {
@@ -48,6 +52,8 @@ internal sealed class HttpConnectionSettings
 
         internal IDictionary<string, object> _properties;
 
+        internal Func<string, int, CancellationToken, ValueTask<Stream>> _customConnect = ConnectHelper.ConnectAsync;
+
         public HttpConnectionSettings()
         {
             bool allowHttp2 = AllowHttp2;
@@ -88,6 +94,7 @@ public HttpConnectionSettings CloneAndNormalize()
                 _useCookies = _useCookies,
                 _useProxy = _useProxy,
                 _allowUnencryptedHttp2 = _allowUnencryptedHttp2,
+                _customConnect = _customConnect
             };
         }
 
diff --git a/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/SocketsHttpHandler.cs b/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/SocketsHttpHandler.cs
index 9de8d147c7bb..d5484b15d460 100644
--- a/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/SocketsHttpHandler.cs
+++ b/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/SocketsHttpHandler.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Generic;
+using System.IO;
 using System.Net.Security;
 using System.Threading;
 using System.Threading.Tasks;
@@ -32,6 +33,16 @@ private void CheckDisposedOrStarted()
             }
         }
 
+        public Func<string, int, CancellationToken, ValueTask<Stream>> ConnectCallback
+        {
+            get => _settings._customConnect;
+            set
+            {
+                CheckDisposedOrStarted();
+                _settings._customConnect = value;
+            }
+        }
+
         public bool UseCookies
         {
             get => _settings._useCookies;
diff --git a/src/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.cs b/src/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.cs
index d10679ea5be2..847299c0a071 100644
--- a/src/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.cs
+++ b/src/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.cs
@@ -2689,5 +2689,41 @@ public async Task GetAsync_InvalidUrl_ExpectedExceptionThrown()
                 await Assert.ThrowsAsync<HttpRequestException>(() => client.GetStringAsync(invalidUri));
             }
         }
+
+        [Fact]
+        public async Task ConnectCallback_Success()
+        {
+            if (!UseSocketsHttpHandler || UseHttp2) return;
+
+            await LoopbackServer.CreateClientAndServerAsync(
+                async uri =>
+                {
+                    bool dialerCalled = false;
+
+                    Func<string, int, CancellationToken, ValueTask<Stream>> dialer = (host, port, token) =>
+                    {
+                        dialerCalled = true;
+
+                        byte[] buffer = Encoding.ASCII.GetBytes("HTTP/1.1 200 OK\r\nConnection: close\r\nContent-Length: 3\r\nContent-Type: text/plain\r\n\r\nfoo");
+
+                        var stream = new MemoryStream(buffer);
+                        var delegateStream = new DelegateStream(canReadFunc: () => true, canWriteFunc: () => true, readFunc: stream.Read, writeFunc: delegate { });
+                        return new ValueTask<Stream>(delegateStream);
+                    };
+
+                    using var handler = new SocketsHttpHandler();
+                    handler.ConnectCallback = dialer;
+
+                    using HttpClient client = CreateHttpClient(handler);
+
+                    // If GetStringAsync fails with a connect timeout, the dialer is not getting called -- it's hitting a loopback socket that will never accept.
+                    string result = await client.GetStringAsync(uri);
+
+                    Assert.Equal("foo", result);
+                    Assert.True(dialerCalled);
+                },
+                server => Task.CompletedTask,
+                new LoopbackServer.Options { ListenBacklog = 0 });
+        }
     }
 }