diff --git a/src/shared/GitHub.Tests/GitHubHostProviderTests.cs b/src/shared/GitHub.Tests/GitHubHostProviderTests.cs
index 338329024..6a8cce07e 100644
--- a/src/shared/GitHub.Tests/GitHubHostProviderTests.cs
+++ b/src/shared/GitHub.Tests/GitHubHostProviderTests.cs
@@ -28,46 +28,66 @@ public void GitHubHostProvider_IsGitHubDotCom(string input, bool expected)
         [Theory]
         // We report that we support unencrypted HTTP here so that we can fail and
         // show a helpful error message in the call to `GenerateCredentialAsync` instead.
-        [InlineData("http://github.com", true)]
-        [InlineData("http://gist.github.com", true)]
-        [InlineData("https://github.com", true)]
-        [InlineData("https://gist.github.com", true)]
-        [InlineData("ssh://github.com", false)]
-        [InlineData("https://example.com", false)]
-        public void GitHubHostProvider_IsSupported(string uriString, bool expected)
+        [InlineData("http", "github.com", true)]
+        [InlineData("http", "gist.github.com", true)]
+        [InlineData("ssh", "github.com", false)]
+        [InlineData("https", "example.com", false)]
+
+        [InlineData("https", "github.com", true)]
+        [InlineData("https", "github.con", false)] // No support of phony similar tld.
+        [InlineData("https", "gist.github.con", false)] // No support of phony similar tld.
+        [InlineData("https", "foogithub.com", false)] // No support of non github.com domains.
+        [InlineData("https", "api.github.com", false)] // No support of github.com subdomains.
+        [InlineData("https", "gist.github.com", true)] // Except gists.
+        [InlineData("https", "GiST.GitHub.Com", true)]
+        [InlineData("https", "GitHub.Com", true)]
+
+        [InlineData("http", "github.my-company-server.com", true)]
+        [InlineData("http", "gist.github.my-company-server.com", true)]
+        [InlineData("https", "github.my-company-server.com", true)]
+        [InlineData("https", "gist.github.my-company-server.com", true)]
+        [InlineData("https", "gist.my-company-server.com", false)]
+        [InlineData("https", "my-company-server.com", false)]
+        [InlineData("https", "github.my.company.server.com", true)]
+        [InlineData("https", "foogithub.my-company-server.com", false)]
+        [InlineData("https", "api.github.my-company-server.com", false)]
+        [InlineData("https", "gist.github.my.company.server.com", true)]
+        [InlineData("https", "GitHub.My-Company-Server.Com", true)]
+        [InlineData("https", "GiST.GitHub.My-Company-Server.com", true)]
+        public void GitHubHostProvider_IsSupported(string protocol, string host, bool expected)
         {
-            Uri uri = new Uri(uriString);
-
             var input = new InputArguments(new Dictionary<string, string>
             {
-                ["protocol"] = uri.Scheme,
-                ["host"] = uri.Host,
+                ["protocol"] = protocol,
+                ["host"] = host,
             });
 
-            // Ensure nothing got lost during transformation
-            Assert.Equal(uriString, input.Protocol + "://" + input.Host);
-
             var provider = new GitHubHostProvider(new TestCommandContext());
             Assert.Equal(expected, provider.IsSupported(input));
         }
 
 
         [Theory]
-        [InlineData("https://github.com", "https://github.com")]
-        [InlineData("https://gist.github.com", "https://github.com")]
-        public void GitHubHostProvider_GetCredentialServiceUrl(string uriString, string expectedService)
+        [InlineData("https", "github.com", "https://github.com")]
+        [InlineData("https", "GitHub.Com", "https://github.com")]
+        [InlineData("https", "gist.github.com", "https://github.com")]
+        [InlineData("https", "GiST.GitHub.Com", "https://github.com")]
+        [InlineData("https", "github.my-company-server.com", "https://github.my-company-server.com")]
+        [InlineData("https", "GitHub.My-Company-Server.Com", "https://github.my-company-server.com")]
+        [InlineData("https", "gist.github.my-company-server.com", "https://github.my-company-server.com")]
+        [InlineData("https", "GiST.GitHub.My-Company-Server.Com", "https://github.my-company-server.com")]
+        [InlineData("https", "github.my.company.server.com", "https://github.my.company.server.com")]
+        [InlineData("https", "GitHub.My.Company.Server.Com", "https://github.my.company.server.com")]
+        [InlineData("https", "gist.github.my.company.server.com", "https://github.my.company.server.com")]
+        [InlineData("https", "GiST.GitHub.My.Company.Server.Com", "https://github.my.company.server.com")]
+        public void GitHubHostProvider_GetCredentialServiceUrl(string protocol, string host, string expectedService)
         {
-            Uri uri = new Uri(uriString);
-
             var input = new InputArguments(new Dictionary<string, string>
             {
-                ["protocol"] = uri.Scheme,
-                ["host"] = uri.Host,
+                ["protocol"] = protocol,
+                ["host"] = host,
             });
 
-            // Ensure nothing got lost during transformation
-            Assert.Equal(uriString, input.Protocol + "://" + input.Host);
-
             var provider = new GitHubHostProvider(new TestCommandContext());
             Assert.Equal(expectedService, provider.GetServiceName(input));
         }
@@ -76,8 +96,11 @@ public void GitHubHostProvider_GetCredentialServiceUrl(string uriString, string
         [Theory]
         [InlineData("https://example.com", "oauth", AuthenticationModes.OAuth)]
         [InlineData("https://github.com", "NOT-A-REAL-VALUE", GitHubConstants.DotComAuthenticationModes)]
+        [InlineData("https://GitHub.Com", "NOT-A-REAL-VALUE", GitHubConstants.DotComAuthenticationModes)]
         [InlineData("https://github.com", "none", GitHubConstants.DotComAuthenticationModes)]
+        [InlineData("https://GitHub.Com", "none", GitHubConstants.DotComAuthenticationModes)]
         [InlineData("https://github.com", null, GitHubConstants.DotComAuthenticationModes)]
+        [InlineData("https://GitHub.Com", null, GitHubConstants.DotComAuthenticationModes)]
         public async Task GitHubHostProvider_GetSupportedAuthenticationModes(string uriString, string gitHubAuthModes, AuthenticationModes expectedModes)
         {
             var targetUri = new Uri(uriString);
diff --git a/src/shared/GitHub/GitHubHostProvider.cs b/src/shared/GitHub/GitHubHostProvider.cs
index e1ec4a86b..a85f6ba40 100644
--- a/src/shared/GitHub/GitHubHostProvider.cs
+++ b/src/shared/GitHub/GitHubHostProvider.cs
@@ -52,16 +52,42 @@ public override bool IsSupported(InputArguments input)
                 return false;
             }
 
-            // Split port number and hostname from host input argument
-            input.TryGetHostAndPort(out string hostName, out _);
-
             // We do not support unencrypted HTTP communications to GitHub,
             // but we report `true` here for HTTP so that we can show a helpful
             // error message for the user in `CreateCredentialAsync`.
-            return (StringComparer.OrdinalIgnoreCase.Equals(input.Protocol, "http") ||
-                    StringComparer.OrdinalIgnoreCase.Equals(input.Protocol, "https")) &&
-                   (StringComparer.OrdinalIgnoreCase.Equals(hostName, GitHubConstants.GitHubBaseUrlHost) ||
-                    StringComparer.OrdinalIgnoreCase.Equals(hostName, GitHubConstants.GistBaseUrlHost));
+            if (!StringComparer.OrdinalIgnoreCase.Equals(input.Protocol, "http") &&
+                !StringComparer.OrdinalIgnoreCase.Equals(input.Protocol, "https"))
+            {
+                return false;
+            }
+
+            // Split port number and hostname from host input argument
+            input.TryGetHostAndPort(out string hostName, out _);
+
+            if (StringComparer.OrdinalIgnoreCase.Equals(hostName, GitHubConstants.GitHubBaseUrlHost) ||
+                StringComparer.OrdinalIgnoreCase.Equals(hostName, GitHubConstants.GistBaseUrlHost))
+            {
+                return true;
+            }
+
+            string[] domains = hostName.Split(new char[] { '.' });
+
+            // github[.subdomain].domain.tld
+            if (domains.Length >= 3 &&
+                StringComparer.OrdinalIgnoreCase.Equals(domains[0], "github"))
+            {
+                return true;
+            }
+
+            // gist.github[.subdomain].domain.tld
+            if (domains.Length >= 4 &&
+                StringComparer.OrdinalIgnoreCase.Equals(domains[0], "gist") &&
+                StringComparer.OrdinalIgnoreCase.Equals(domains[1], "github"))
+            {
+                return true;
+            }
+
+            return false;
         }
 
         public override string GetServiceName(InputArguments input)
@@ -264,10 +290,11 @@ private static Uri NormalizeUri(Uri uri)
             }
 
             // Special case for gist.github.com which are git backed repositories under the hood.
-            // Credentials for these repositories are the same as the one stored with "github.com"
-            if (uri.DnsSafeHost.Equals(GitHubConstants.GistBaseUrlHost, StringComparison.OrdinalIgnoreCase))
-            {
-                return new Uri("https://" + GitHubConstants.GitHubBaseUrlHost);
+            // Credentials for these repositories are the same as the one stored with "github.com".
+            // Same for gist.github[.subdomain].domain.tld. The general form was already checked via IsSupported.
+            int firstDot = uri.DnsSafeHost.IndexOf(".");
+            if (firstDot > -1 && uri.DnsSafeHost.Substring(0, firstDot).Equals("gist", StringComparison.OrdinalIgnoreCase)) {
+                return new Uri("https://" + uri.DnsSafeHost.Substring(firstDot+1));
             }
 
             return uri;