diff --git a/Program.cs b/Program.cs
index 8956825..d427b18 100644
--- a/Program.cs
+++ b/Program.cs
@@ -178,6 +178,11 @@ api.MapPost("/suggestions", async ([FromBody] SuggestionRequest request, HttpCon
 
     var player = await GetOrCreatePlayer(ctx, db);
 
+    if (string.IsNullOrWhiteSpace(player.DisplayName))
+    {
+        return Results.BadRequest(new { error = "Set a display name before submitting suggestions." });
+    }
+
     var existingCount = await db.Suggestions.CountAsync(s => s.PlayerId == player.Id);
     if (existingCount >= 3)
     {
@@ -263,6 +268,9 @@ api.MapPost("/votes", async ([FromBody] VoteRequest request, HttpContext ctx, Ap
 
     var player = await GetOrCreatePlayer(ctx, db);
 
+    if (string.IsNullOrWhiteSpace(player.DisplayName))
+        return Results.BadRequest(new { error = "Set a display name before voting." });
+
     var suggestionExists = await db.Suggestions.AnyAsync(s => s.Id == request.SuggestionId);
     if (!suggestionExists)
         return Results.BadRequest(new { error = "Suggestion not found." });
diff --git a/wwwroot/app.js b/wwwroot/app.js
index 7a9a1a9..c1add84 100644
--- a/wwwroot/app.js
+++ b/wwwroot/app.js
@@ -55,6 +55,7 @@ async function loadState() {
   if ($("player-id")) {
     $("player-id").textContent = `Player ID: ${me.id}`;
   }
+  applyNameRequirementUI();
 }
 
 async function loadSuggestData() {
@@ -97,6 +98,7 @@ function renderPhasePill() {
   if (phaseSelect && !phaseSelect.dataset.userEditing) {
     phaseSelect.value = state.phase || "Suggest";
   }
+  applyNameRequirementUI();
 }
 
 function renderCounts() {
@@ -216,6 +218,7 @@ function setupHandlers() {
       state.me = me;
       nameInput.dataset.userEditing = "";
       toast("Saved name");
+      applyNameRequirementUI();
     } catch (err) {
       toast(err.message, true);
     }
@@ -335,6 +338,31 @@ function openLightbox(url, title) {
   document.body.appendChild(overlay);
 }
 
+function applyNameRequirementUI() {
+  const requiresName = !state.me?.displayName?.trim();
+  const warning = $("name-warning");
+  if (warning) warning.classList.toggle("hidden", !requiresName);
+
+  const suggestForm = $("suggest-form");
+  if (suggestForm) {
+    suggestForm.querySelectorAll("input,textarea,button").forEach(el => {
+      if (el.id === "save-name") return;
+      el.disabled = requiresName;
+    });
+    suggestForm.classList.toggle("disabled-form", requiresName);
+  }
+
+  const voteList = $("vote-list");
+  if (voteList) {
+    voteList.querySelectorAll("input[type=range]").forEach(el => el.disabled = requiresName);
+    voteList.classList.toggle("disabled-form", requiresName);
+  }
+
+  if (requiresName && state.phase !== "Suggest") {
+    toast("Enter a name to continue.", true);
+  }
+}
+
 async function main() {
   setupHandlers();
   try {
diff --git a/wwwroot/styles.css b/wwwroot/styles.css
index 3034d1c..83306d8 100644
--- a/wwwroot/styles.css
+++ b/wwwroot/styles.css
@@ -106,6 +106,8 @@ button.ghost {
 
 .label { color: #9ca3af; font-size: 12px; }
 .hint { color: #9ca3af; font-size: 12px; margin: 8px 0 0; }
+.hint.warning { color: #f59e0b; }
+.disabled-form { opacity: 0.5; pointer-events: none; }
 
 .card-grid {
   display: grid;