diff --git a/provider/common/attrvalidators/list.go b/provider/common/attrvalidators/list.go
index 138a9955..0ff0e370 100644
--- a/provider/common/attrvalidators/list.go
+++ b/provider/common/attrvalidators/list.go
@@ -26,5 +26,4 @@ func NewListValidator(desc string, validator func(ctx context.Context, req valid
 		desc:      desc,
 		validator: validator,
 	}
-
 }
diff --git a/provider/identityprovider/htpasswd.go b/provider/identityprovider/htpasswd.go
index 8bdb0119..5483ac46 100644
--- a/provider/identityprovider/htpasswd.go
+++ b/provider/identityprovider/htpasswd.go
@@ -2,6 +2,7 @@ package identityprovider
 
 import (
 	"context"
+	"fmt"
 	"regexp"
 
 	"github.com/hashicorp/terraform-plugin-framework-validators/listvalidator"
@@ -9,6 +10,7 @@ import (
 	"github.com/hashicorp/terraform-plugin-framework/resource/schema"
 	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
 	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/terraform-redhat/terraform-provider-rhcs/provider/common/attrvalidators"
 
 	cmv1 "github.com/openshift-online/ocm-sdk-go/clustersmgmt/v1"
 )
@@ -53,6 +55,7 @@ var htpasswdSchema = map[string]schema.Attribute{
 		},
 		Validators: []validator.List{
 			listvalidator.SizeAtLeast(1),
+			uniqueUsernameValidator(),
 		},
 		Required: true,
 	},
@@ -86,3 +89,24 @@ func CreateHTPasswdIDPBuilder(ctx context.Context, state *HTPasswdIdentityProvid
 	builder.Users(userListBuilder)
 	return builder
 }
+
+func uniqueUsernameValidator() validator.List {
+	return attrvalidators.NewListValidator("userlist unique username", func(ctx context.Context, req validator.ListRequest, resp *validator.ListResponse) {
+		usersList := req.ConfigValue
+		htusers := []HTPasswdUser{}
+		err := usersList.ElementsAs(ctx, &htusers, true)
+		if err != nil {
+			resp.Diagnostics.AddAttributeError(req.Path, "Invalid list conversion", "Failed to parse userlist")
+			return
+		}
+		usernames := make(map[string]bool)
+		for _, user := range htusers {
+			if _, ok := usernames[user.Username.ValueString()]; ok {
+				// Username already exists
+				resp.Diagnostics.AddAttributeError(req.Path, fmt.Sprintf("Found duplicate username: '%s'", user.Username.ValueString()), "Usernames in HTPasswd user list must be unique")
+				return
+			}
+			usernames[user.Username.ValueString()] = true
+		}
+	})
+}
diff --git a/subsystem/identity_provider_resource_test.go b/subsystem/identity_provider_resource_test.go
index 5ffa7765..f76e7e81 100644
--- a/subsystem/identity_provider_resource_test.go
+++ b/subsystem/identity_provider_resource_test.go
@@ -94,6 +94,28 @@ var _ = Describe("Identity provider creation", func() {
                       users = []
 	    	        }
 	    	      }
+	    	    `)
+				Expect(terraform.Apply()).ToNot(BeZero())
+			})
+			It("Can't create a 'htpasswd' identity provider. duplication of username", func() {
+				// Run the apply command:
+				terraform.Source(`
+	    	      resource "rhcs_identity_provider" "my_ip" {
+	    	        cluster = "123"
+	    	        name    = "my-ip"
+	    	        htpasswd = {
+                      users = [
+                        {
+                            username = "foo"
+                            password = "` + htpasswdValidPass + `"
+                        },
+                        {
+                            username = "foo"
+                            password = "` + htpasswdValidPass + `"
+                        }
+                      ]
+	    	        }
+	    	      }
 	    	    `)
 				Expect(terraform.Apply()).ToNot(BeZero())
 			})