diff --git a/.spelling b/.spelling
index 802cdb665f7..3207ea808fd 100644
--- a/.spelling
+++ b/.spelling
@@ -1239,5 +1239,7 @@ v6.0.
 
 #region test/tools/WebListener/README.md Overrides
  - test/tools/WebListener/README.md
+Auth
+NTLM
 ResponseHeaders
 #endregion
diff --git a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/Common/WebRequestPSCmdlet.Common.cs b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/Common/WebRequestPSCmdlet.Common.cs
index 69542eb16ef..1b142f273f4 100644
--- a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/Common/WebRequestPSCmdlet.Common.cs
+++ b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/Common/WebRequestPSCmdlet.Common.cs
@@ -354,6 +354,12 @@ internal virtual void ValidateParameters()
                                                        "WebCmdletAllowUnencryptedAuthenticationRequiredException");
                 ThrowTerminatingError(error);
             }
+            if (!AllowUnencryptedAuthentication && (null != Credential || UseDefaultCredentials) && (Uri.Scheme != "https"))
+            {
+                ErrorRecord error = GetValidationError(WebCmdletStrings.AllowUnencryptedAuthenticationRequired,
+                                                       "WebCmdletAllowUnencryptedAuthenticationRequiredException");
+                ThrowTerminatingError(error);
+            }
 
             // credentials
             if (UseDefaultCredentials && (null != Credential))
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Utility/WebCmdlets.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Utility/WebCmdlets.Tests.ps1
index 8dc1b1aaaef..c4560daae04 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Utility/WebCmdlets.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Utility/WebCmdlets.Tests.ps1
@@ -1312,6 +1312,8 @@ Describe "Invoke-WebRequest tests" -Tags "Feature" {
             $credential = [pscredential]::new("testuser",$token)
             $httpUri = Get-WebListenerUrl -Test 'Get'
             $httpsUri = Get-WebListenerUrl -Test 'Get' -Https
+            $httpBasicUri = Get-WebListenerUrl -Test 'Auth' -TestValue 'Basic'
+            $httpsBasicUri = Get-WebListenerUrl -Test 'Auth' -TestValue 'Basic' -Https
             $testCases = @(
                 @{Authentication = "bearer"}
                 @{Authentication = "OAuth"}
@@ -1412,6 +1414,83 @@ Describe "Invoke-WebRequest tests" -Tags "Feature" {
 
             $result.Headers.Authorization | Should BeExactly "Bearer testpassword"
         }
+
+        It "Verifies Invoke-WebRequest Negotiated -Credential over HTTPS" {
+            $params = @{
+                Uri = $httpsBasicUri
+                Credential = $credential
+                SkipCertificateCheck = $true
+            }
+            $Response = Invoke-WebRequest @params
+            $result = $response.Content | ConvertFrom-Json
+
+            $result.Headers.Authorization | Should BeExactly "Basic dGVzdHVzZXI6dGVzdHBhc3N3b3Jk"
+        }
+
+        It "Verifies Invoke-WebRequest Negotiated -Credential Requires HTTPS" {
+            $params = @{
+                Uri = $httpBasicUri
+                Credential = $credential
+                ErrorAction = 'Stop'
+            }
+            { Invoke-WebRequest @params } | ShouldBeErrorId "WebCmdletAllowUnencryptedAuthenticationRequiredException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand"
+        }
+
+        It "Verifies Invoke-WebRequest Negotiated -Credential Can use HTTP with -AllowUnencryptedAuthentication" {
+            $params = @{
+                Uri = $httpBasicUri
+                Credential = $credential
+                AllowUnencryptedAuthentication = $true
+            }
+            $Response = Invoke-WebRequest @params
+            $result = $response.Content | ConvertFrom-Json
+
+            $result.Headers.Authorization | Should BeExactly "Basic dGVzdHVzZXI6dGVzdHBhc3N3b3Jk"
+        }
+
+        # UseDefaultCredentials is only reliably testable on Windows
+        It "Verifies Invoke-WebRequest Negotiated -UseDefaultCredentials with '<AuthType>' over HTTPS" -Skip:$(!$IsWindows) -TestCases @(
+            @{AuthType = 'NTLM'}
+            @{AuthType = 'Negotiate'}
+        ) {
+            param($AuthType)
+            $params = @{
+                Uri = Get-WebListenerUrl -Test 'Auth' -TestValue $AuthType -Https
+                UseDefaultCredentials = $true
+                SkipCertificateCheck = $true
+            }
+            $Response = Invoke-WebRequest @params
+            $result = $response.Content | ConvertFrom-Json
+
+            $result.Headers.Authorization | Should Match "^$AuthType "
+        }
+
+        # The error condition can at least be tested on all platforms.
+        It "Verifies Invoke-WebRequest Negotiated -UseDefaultCredentials Requires HTTPS" {
+            $params = @{
+                Uri = $httpUri
+                UseDefaultCredentials = $true
+                ErrorAction = 'Stop'
+            }
+            { Invoke-WebRequest @params } | ShouldBeErrorId "WebCmdletAllowUnencryptedAuthenticationRequiredException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand"
+        }
+
+        # UseDefaultCredentials is only reliably testable on Windows
+        It "Verifies Invoke-WebRequest Negotiated -UseDefaultCredentials with '<AuthType>' Can use HTTP with -AllowUnencryptedAuthentication" -Skip:$(!$IsWindows) -TestCases @(
+            @{AuthType = 'NTLM'}
+            @{AuthType = 'Negotiate'}
+        ) {
+            param($AuthType)
+            $params = @{
+                Uri = Get-WebListenerUrl -Test 'Auth' -TestValue $AuthType
+                UseDefaultCredentials = $true
+                AllowUnencryptedAuthentication = $true
+            }
+            $Response = Invoke-WebRequest @params
+            $result = $response.Content | ConvertFrom-Json
+
+            $result.Headers.Authorization | Should Match "^$AuthType "
+        }
     }
 
     BeforeEach {
@@ -2233,6 +2312,8 @@ Describe "Invoke-RestMethod tests" -Tags "Feature" {
             $credential = [pscredential]::new("testuser",$token)
             $httpUri = Get-WebListenerUrl -Test 'Get'
             $httpsUri = Get-WebListenerUrl -Test 'Get' -Https
+            $httpBasicUri = Get-WebListenerUrl -Test 'Auth' -TestValue 'Basic'
+            $httpsBasicUri = Get-WebListenerUrl -Test 'Auth' -TestValue 'Basic' -Https
             $testCases = @(
                 @{Authentication = "bearer"}
                 @{Authentication = "OAuth"}
@@ -2330,6 +2411,79 @@ Describe "Invoke-RestMethod tests" -Tags "Feature" {
 
             $result.Headers.Authorization | Should BeExactly "Bearer testpassword"
         }
+
+        It "Verifies Invoke-RestMethod Negotiated -Credential over HTTPS" {
+            $params = @{
+                Uri = $httpsBasicUri
+                Credential = $credential
+                SkipCertificateCheck = $true
+            }
+            $result = Invoke-RestMethod @params
+
+            $result.Headers.Authorization | Should BeExactly "Basic dGVzdHVzZXI6dGVzdHBhc3N3b3Jk"
+        }
+
+        It "Verifies Invoke-RestMethod Negotiated -Credential Requires HTTPS" {
+            $params = @{
+                Uri = $httpBasicUri
+                Credential = $credential
+                ErrorAction = 'Stop'
+            }
+            { Invoke-RestMethod @params } | ShouldBeErrorId "WebCmdletAllowUnencryptedAuthenticationRequiredException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand"
+        }
+
+        It "Verifies Invoke-RestMethod Negotiated -Credential Can use HTTP with -AllowUnencryptedAuthentication" {
+            $params = @{
+                Uri = $httpBasicUri
+                Credential = $credential
+                AllowUnencryptedAuthentication = $true
+            }
+            $result = Invoke-RestMethod @params
+
+            $result.Headers.Authorization | Should BeExactly "Basic dGVzdHVzZXI6dGVzdHBhc3N3b3Jk"
+        }
+
+        # UseDefaultCredentials is only reliably testable on Windows
+        It "Verifies Invoke-RestMethod Negotiated -UseDefaultCredentials with '<AuthType>' over HTTPS" -Skip:$(!$IsWindows) -TestCases @(
+            @{AuthType = 'NTLM'}
+            @{AuthType = 'Negotiate'}
+        ) {
+            param($AuthType)
+            $params = @{
+                Uri = Get-WebListenerUrl -Test 'Auth' -TestValue $AuthType -Https
+                UseDefaultCredentials = $true
+                SkipCertificateCheck = $true
+            }
+            $result = Invoke-RestMethod @params
+
+            $result.Headers.Authorization | Should Match "^$AuthType "
+        }
+
+        # The error condition can at least be tested on all platforms.
+        It "Verifies Invoke-RestMethod Negotiated -UseDefaultCredentials Requires HTTPS" {
+            $params = @{
+                Uri = $httpUri
+                UseDefaultCredentials = $true
+                ErrorAction = 'Stop'
+            }
+            { Invoke-RestMethod @params } | ShouldBeErrorId "WebCmdletAllowUnencryptedAuthenticationRequiredException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand"
+        }
+
+        # UseDefaultCredentials is only reliably testable on Windows
+        It "Verifies Invoke-RestMethod Negotiated -UseDefaultCredentials with '<AuthType>' Can use HTTP with -AllowUnencryptedAuthentication" -Skip:$(!$IsWindows) -TestCases @(
+            @{AuthType = 'NTLM'}
+            @{AuthType = 'Negotiate'}
+        ) {
+            param($AuthType)
+            $params = @{
+                Uri = Get-WebListenerUrl -Test 'Auth' -TestValue $AuthType
+                UseDefaultCredentials = $true
+                AllowUnencryptedAuthentication = $true
+            }
+            $result = Invoke-RestMethod @params
+
+            $result.Headers.Authorization | Should Match "^$AuthType "
+        }
     }
 
     BeforeEach {
diff --git a/test/tools/Modules/WebListener/WebListener.psm1 b/test/tools/Modules/WebListener/WebListener.psm1
index a3125d07c6b..3aa83c7a81e 100644
--- a/test/tools/Modules/WebListener/WebListener.psm1
+++ b/test/tools/Modules/WebListener/WebListener.psm1
@@ -113,6 +113,7 @@ function Get-WebListenerUrl {
     param (
         [switch]$Https,
         [ValidateSet(
+            'Auth',
             'Cert',
             'Compression',
             'Delay',
diff --git a/test/tools/WebListener/Controllers/AuthController.cs b/test/tools/WebListener/Controllers/AuthController.cs
new file mode 100644
index 00000000000..c75eff0b7e7
--- /dev/null
+++ b/test/tools/WebListener/Controllers/AuthController.cs
@@ -0,0 +1,73 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Http.Extensions;
+using Microsoft.Extensions.Primitives;
+using mvc.Models;
+
+namespace mvc.Controllers
+{
+    public class AuthController : Controller
+    {
+        public JsonResult Basic()
+        {
+            StringValues authorization;
+            if (Request.Headers.TryGetValue("Authorization", out authorization))
+            {
+                var getController = new GetController();
+                getController.ControllerContext = this.ControllerContext;
+                return getController.Index();
+            }
+            else
+            {
+                Response.Headers.Add("WWW-Authenticate","Basic realm=\"WebListener\"");
+                Response.StatusCode = 401;
+                return Json("401 Unauthorized");
+            }
+        }
+
+        public JsonResult Negotiate()
+        {
+            StringValues authorization;
+            if (Request.Headers.TryGetValue("Authorization", out authorization))
+            {
+                var getController = new GetController();
+                getController.ControllerContext = this.ControllerContext;
+                return getController.Index();
+            }
+            else
+            {
+                Response.Headers.Add("WWW-Authenticate","Negotiate");
+                Response.StatusCode = 401;
+                return Json("401 Unauthorized");
+            }
+        }
+
+        public JsonResult Ntlm()
+        {
+            StringValues authorization;
+            if (Request.Headers.TryGetValue("Authorization", out authorization))
+            {
+                var getController = new GetController();
+                getController.ControllerContext = this.ControllerContext;
+                return getController.Index();
+            }
+            else
+            {
+                Response.Headers.Add("WWW-Authenticate","NTLM");
+                Response.StatusCode = 401;
+                return Json("401 Unauthorized");
+            }
+        }
+
+        public IActionResult Error()
+        {
+            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
+        }
+    }
+}
diff --git a/test/tools/WebListener/README.md b/test/tools/WebListener/README.md
index 04dbd20ccb5..5aca1cc4def 100644
--- a/test/tools/WebListener/README.md
+++ b/test/tools/WebListener/README.md
@@ -34,6 +34,76 @@ $Listener = Start-WebListener -HttpPort 8083 -HttpsPort 8084
 
 Returns a static HTML page containing links and descriptions of the available tests in WebListener. This can be used as a default or general test where no specific test functionality or return data is required.
 
+## /Auth/Basic/
+
+Provides a mock Basic authentication challenge. If a basic authorization header is sent, then the same results as /Get/ are returned.
+
+```powershell
+$credential = Get-Credential
+$uri = Get-WebListenerUrl -Test 'Auth' -TestValue 'Basic' -Https
+Invoke-RestMethod -Uri $uri -Credential $credential -SkipCertificateCheck
+```
+
+```json
+{
+    "headers":{
+        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Microsoft Windows 10.0.15063; en-US) PowerShell/6.0.0",
+        "Connection": "Keep-Alive",
+        "Authorization": "Basic dGVzdHVzZXI6dGVzdHBhc3N3b3Jk", 
+        "Host": "localhost:8084"
+    },
+    "origin": "127.0.0.1",
+    "args": {},
+    "url": "https://localhost:8084/Auth/Basic"
+}
+```
+
+## /Auth/Negotiate/
+
+Provides a mock Negotiate authentication challenge. If a basic authorization header is sent, then the same results as /Get/ are returned.
+
+```powershell
+$uri = Get-WebListenerUrl -Test 'Auth' -TestValue 'Negotiate' -Https
+Invoke-RestMethod -Uri $uri -UseDefaultCredential -SkipCertificateCheck
+```
+
+```json
+{
+    "headers":{
+        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Microsoft Windows 10.0.15063; en-US) PowerShell/6.0.0",
+        "Connection": "Keep-Alive",
+        "Authorization": "Negotiate jjaguasgtisi7tiqkagasjjajvs", 
+        "Host": "localhost:8084"
+    },
+    "origin": "127.0.0.1",
+    "args": {},
+    "url": "https://localhost:8084/Auth/Negotiate"
+}
+```
+
+## /Auth/NTLM/
+
+Provides a mock NTLM authentication challenge. If a basic authorization header is sent, then the same results as /Get/ are returned.
+
+```powershell
+$uri = Get-WebListenerUrl -Test 'Auth' -TestValue 'NTLM' -Https
+Invoke-RestMethod -Uri $uri -UseDefaultCredential -SkipCertificateCheck
+```
+
+```json
+{
+    "headers":{
+        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Microsoft Windows 10.0.15063; en-US) PowerShell/6.0.0",
+        "Connection": "Keep-Alive",
+        "Authorization": "NTLM jjaguasgtisi7tiqkagasjjajvs", 
+        "Host": "localhost:8084"
+    },
+    "origin": "127.0.0.1",
+    "args": {},
+    "url": "https://localhost:8084/Auth/NTLM"
+}
+```
+
 ## /Cert/
 
 Returns a JSON object containing the details of the Client Certificate if one is provided in the request.
diff --git a/test/tools/WebListener/Views/Home/Index.cshtml b/test/tools/WebListener/Views/Home/Index.cshtml
index 6c88ce5e0a3..13699a36b33 100644
--- a/test/tools/WebListener/Views/Home/Index.cshtml
+++ b/test/tools/WebListener/Views/Home/Index.cshtml
@@ -1,6 +1,9 @@
 <h1>Available Tests</h1>
 <ul>
     <li><a href="/">/</a> - This page</li>
+    <li><a href="/Auth/Basic/">/Auth/Basic/</a> - Basic Authentication</li>
+    <li><a href="/Auth/Negotiate/">/Auth/Negotiate/</a> - Negotiate Authentication</li>
+    <li><a href="/Auth/NTLM/">/Auth/NTLM/</a> - NTLM Authentication</li>
     <li><a href="/Cert/">/Cert/</a> - Client Certificate Details</li>
     <li><a href="/Compression/Deflate/">/Compression/Deflate/</a> - Returns deflate compressed response</li>
     <li><a href="/Compression/GZip/">/Compression/Gzip/</a> - Returns gzip compressed response</li>