diff --git a/samples/Mvc.Server/Startup.cs b/samples/Mvc.Server/Startup.cs
index 256ccc13..4aeb6a95 100644
--- a/samples/Mvc.Server/Startup.cs
+++ b/samples/Mvc.Server/Startup.cs
@@ -48,6 +48,9 @@ namespace Mvc.Server {
                 .AllowPasswordFlow()
                 .AllowRefreshTokenFlow()
 
+                // Make the "client_id" parameter mandatory when sending a token request.
+                .RequireClientIdentification()
+
                 // During development, you can disable the HTTPS requirement.
                 .DisableHttpsRequirement()
 
diff --git a/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Exchange.cs b/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Exchange.cs
index 4d830820..24921c9e 100644
--- a/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Exchange.cs
+++ b/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Exchange.cs
@@ -79,11 +79,24 @@ namespace OpenIddict.Infrastructure {
             // See http://openid.net/specs/openid-connect-core-1_0.html#RefreshingAccessToken
             // and https://tools.ietf.org/html/rfc6749#section-6 for more information.
 
-            // At this stage, skip client authentication if the client identifier is missing.
+            // At this stage, skip client authentication if the client identifier is missing
+            // or reject the token request if client identification is set as required.
             // Note: the OpenID Connect server middleware will automatically ensure that
             // the calling application cannot use an authorization code or a refresh token
             // if it's not the intended audience, even if client authentication was skipped.
             if (string.IsNullOrEmpty(context.ClientId)) {
+                // Reject the request if client identification is mandatory.
+                if (services.Options.RequireClientIdentification) {
+                    services.Logger.LogError("The token request was rejected becaused the " +
+                                             "mandatory client_id parameter was missing or empty.");
+
+                    context.Reject(
+                        error: OpenIdConnectConstants.Errors.InvalidRequest,
+                        description: "The mandatory 'client_id' parameter was missing.");
+
+                    return;
+                }
+
                 services.Logger.LogInformation("The token request validation process was skipped " +
                                                "because the client_id parameter was missing or empty.");
 
diff --git a/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Revocation.cs b/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Revocation.cs
index 9c24f466..c0da2164 100644
--- a/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Revocation.cs
+++ b/src/OpenIddict.Core/Infrastructure/OpenIddictProvider.Revocation.cs
@@ -31,11 +31,24 @@ namespace OpenIddict.Infrastructure {
                 return;
             }
 
-            // Skip client authentication if the client identifier is missing.
+            // Skip client authentication if the client identifier is missing or reject
+            // the revocation request if client identification is set as required.
             // Note: the OpenID Connect server middleware will automatically ensure that
             // the calling application cannot revoke a refresh token if it's not
             // the intended audience, even if client authentication was skipped.
             if (string.IsNullOrEmpty(context.ClientId)) {
+                // Reject the request if client identification is mandatory.
+                if (services.Options.RequireClientIdentification) {
+                    services.Logger.LogError("The revocation request was rejected becaused the " +
+                                             "mandatory client_id parameter was missing or empty.");
+
+                    context.Reject(
+                        error: OpenIdConnectConstants.Errors.InvalidRequest,
+                        description: "The mandatory 'client_id' parameter was missing.");
+
+                    return;
+                }
+
                 services.Logger.LogInformation("The revocation request validation process was skipped " +
                                                "because the client_id parameter was missing or empty.");
 
diff --git a/src/OpenIddict.Core/OpenIddictBuilder.cs b/src/OpenIddict.Core/OpenIddictBuilder.cs
index b6f1a638..60886652 100644
--- a/src/OpenIddict.Core/OpenIddictBuilder.cs
+++ b/src/OpenIddict.Core/OpenIddictBuilder.cs
@@ -573,6 +573,16 @@ namespace Microsoft.AspNetCore.Builder {
             return Configure(options => options.UserinfoEndpointPath = path);
         }
 
+        /// <summary>
+        /// Makes client identification mandatory so that token and revocation
+        /// requests that don't specify a client_id are automatically rejected.
+        /// Note: enabling this option doesn't prevent public clients from using
+        /// the token and revocation endpoints, but specifying a client_id is required.
+        /// </summary>
+        public virtual OpenIddictBuilder RequireClientIdentification() {
+            return Configure(options => options.RequireClientIdentification = true);
+        }
+
         /// <summary>
         /// Sets the access token lifetime, after which client applications must retrieve
         /// a new access token by making a grant_type=refresh_token token request
diff --git a/src/OpenIddict.Core/OpenIddictOptions.cs b/src/OpenIddict.Core/OpenIddictOptions.cs
index 5f4d2cf4..3d156175 100644
--- a/src/OpenIddict.Core/OpenIddictOptions.cs
+++ b/src/OpenIddict.Core/OpenIddictOptions.cs
@@ -7,7 +7,6 @@
 using System;
 using System.Collections.Generic;
 using AspNet.Security.OpenIdConnect.Server;
-using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Caching.Distributed;
 
 namespace OpenIddict {
@@ -36,5 +35,12 @@ namespace OpenIddict {
         /// Gets the list of the OpenIddict modules registered in the application.
         /// </summary>
         public ICollection<OpenIddictModule> Modules { get; } = new List<OpenIddictModule>();
+
+        /// <summary>
+        /// Gets or sets a boolean determining whether client identification is required.
+        /// Enabling this option requires registering a client application and sending a
+        /// valid client_id when communicating with the token and revocation endpoints.
+        /// </summary>
+        public bool RequireClientIdentification { get; set; }
     }
 }