diff --git a/ChessCubing.App/Models/Users/AdminUpdateUserRequest.cs b/ChessCubing.App/Models/Users/AdminUpdateUserRequest.cs
index ab38e62..fdd1a60 100644
--- a/ChessCubing.App/Models/Users/AdminUpdateUserRequest.cs
+++ b/ChessCubing.App/Models/Users/AdminUpdateUserRequest.cs
@@ -2,8 +2,6 @@ namespace ChessCubing.App.Models.Users;
 
 public sealed class AdminUpdateUserRequest
 {
-    public string Username { get; set; } = string.Empty;
-
     public string? Email { get; set; }
 
     public string? FirstName { get; set; }
diff --git a/ChessCubing.App/Pages/AdminPage.razor b/ChessCubing.App/Pages/AdminPage.razor
index 2bb1cfe..27bea0f 100644
--- a/ChessCubing.App/Pages/AdminPage.razor
+++ b/ChessCubing.App/Pages/AdminPage.razor
@@ -308,7 +308,11 @@
                 <div class="admin-form-grid admin-edit-form-grid">
                     <label class="field">
                         <span>Nom d'utilisateur</span>
-                        <InputText @bind-Value="EditFormModel.Username" />
+                        <InputText @bind-Value="EditFormModel.Username"
+                                   readonly
+                                   aria-readonly="true"
+                                   title="Le nom d'utilisateur ne peut pas etre modifie."
+                                   class="admin-readonly-field" />
                         <ValidationMessage For="@(() => EditFormModel.Username)" />
                     </label>
 
@@ -789,7 +793,6 @@
         {
             var payload = new AdminUpdateUserRequest
             {
-                Username = EditFormModel.Username ?? string.Empty,
                 Email = EditFormModel.Email,
                 FirstName = EditFormModel.FirstName,
                 LastName = EditFormModel.LastName,
diff --git a/ChessCubing.Server/Admin/AdminUserContracts.cs b/ChessCubing.Server/Admin/AdminUserContracts.cs
index 5d122b1..bafc67d 100644
--- a/ChessCubing.Server/Admin/AdminUserContracts.cs
+++ b/ChessCubing.Server/Admin/AdminUserContracts.cs
@@ -70,8 +70,6 @@ public sealed class AdminUserDetailResponse
 
 public sealed class AdminUpdateUserRequest
 {
-    public string Username { get; init; } = string.Empty;
-
     public string? Email { get; init; }
 
     public string? FirstName { get; init; }
diff --git a/ChessCubing.Server/Program.cs b/ChessCubing.Server/Program.cs
index 69e3fda..43e9469 100644
--- a/ChessCubing.Server/Program.cs
+++ b/ChessCubing.Server/Program.cs
@@ -251,8 +251,9 @@ adminGroup.MapPut("/users/{subject}", async Task<IResult> (
 {
     try
     {
+        var existingIdentity = await keycloak.GetAdminUserAsync(subject, cancellationToken);
         var normalized = NormalizeAdminUpdate(request);
-        var fallbackDisplayName = BuildIdentityDisplayNameFromParts(normalized.FirstName, normalized.LastName, normalized.Username);
+        var fallbackDisplayName = BuildIdentityDisplayNameFromParts(normalized.FirstName, normalized.LastName, existingIdentity.Username);
         var siteProfileRequest = new UpdateUserProfileRequest
         {
             DisplayName = request.DisplayName,
@@ -268,7 +269,7 @@ adminGroup.MapPut("/users/{subject}", async Task<IResult> (
         var updatedIdentity = await keycloak.UpdateAdminUserAsync(
             subject,
             new AdminIdentityUserUpdateRequest(
-                normalized.Username,
+                existingIdentity.Username,
                 normalized.Email,
                 normalized.FirstName,
                 normalized.LastName,
@@ -421,13 +422,11 @@ static AdminUserDetailResponse MapAdminDetail(AdminIdentityUser identity, UserPr
 
 static NormalizedAdminUserUpdate NormalizeAdminUpdate(AdminUpdateUserRequest request)
 {
-    var username = NormalizeRequiredValue(request.Username, "nom d'utilisateur", 120);
     var email = NormalizeEmail(request.Email);
     var firstName = NormalizeOptionalValue(request.FirstName, "prenom", 120);
     var lastName = NormalizeOptionalValue(request.LastName, "nom", 120);
 
     return new NormalizedAdminUserUpdate(
-        username,
         email,
         firstName,
         lastName,
@@ -575,7 +574,6 @@ static async Task SignInAsync(HttpContext httpContext, KeycloakUserInfo userInfo
 }
 
 sealed record NormalizedAdminUserUpdate(
-    string Username,
     string? Email,
     string? FirstName,
     string? LastName,
diff --git a/styles.css b/styles.css
index deb230e..cfdab86 100644
--- a/styles.css
+++ b/styles.css
@@ -1868,6 +1868,14 @@ body.site-menu-hidden .site-menu-shell {
   min-height: 3.3rem;
 }
 
+.admin-edit-modal-card input[readonly],
+.admin-readonly-field {
+  color: rgba(255, 255, 255, 0.86);
+  background: rgba(255, 255, 255, 0.025);
+  border-color: rgba(255, 255, 255, 0.12);
+  cursor: default;
+}
+
 .admin-edit-modal-card .profile-feedback {
   margin-bottom: 0.55rem;
   padding: 0.65rem 0.8rem;