diff --git a/bincio/serve/server.py b/bincio/serve/server.py
index db95d01..e0887e5 100644
--- a/bincio/serve/server.py
+++ b/bincio/serve/server.py
@@ -437,6 +437,37 @@ async def admin_jobs(bincio_session: Optional[str] = Cookie(default=None)) -> JS
     return JSONResponse(jobs)
 
 
+@app.delete("/api/admin/users/{handle}/activities")
+async def admin_delete_activities(
+    handle: str,
+    bincio_session: Optional[str] = Cookie(default=None),
+) -> JSONResponse:
+    """Delete all activity JSON files for a user and wipe the merged cache."""
+    _require_admin(bincio_session)
+    user_dir = _get_data_dir() / handle
+    if not user_dir.is_dir():
+        raise HTTPException(404, f"No data directory for user '{handle}'")
+
+    deleted = 0
+    activities_dir = user_dir / "activities"
+    if activities_dir.is_dir():
+        for f in activities_dir.glob("*.json"):
+            f.unlink()
+            deleted += 1
+
+    # Wipe merged cache and top-level index so they don't show stale data
+    import shutil
+    merged_dir = user_dir / "_merged"
+    if merged_dir.exists():
+        shutil.rmtree(merged_dir)
+    index_file = user_dir / "index.json"
+    if index_file.exists():
+        index_file.unlink()
+
+    _trigger_rebuild(handle)
+    return JSONResponse({"ok": True, "deleted": deleted})
+
+
 # ── Write API (ported from bincio edit, auth-gated) ───────────────────────────
 
 def _user_data_dir(handle: str) -> Path:
diff --git a/site/src/layouts/Base.astro b/site/src/layouts/Base.astro
index befcaae..4989589 100644
--- a/site/src/layouts/Base.astro
+++ b/site/src/layouts/Base.astro
@@ -200,6 +200,13 @@ try {
               title=""
               class="text-xs px-2 py-0.5 rounded-full bg-amber-900/60 text-amber-300 border border-amber-700/50 animate-pulse cursor-default"
             ></span>
+            <!-- Admin link — hidden until confirmed admin -->
+            <a
+              id="nav-admin"
+              href={`${baseUrl}admin/`}
+              style="display:none"
+              class="text-xs text-zinc-500 hover:text-white transition-colors px-1"
+            >Admin</a>
 
             <!-- Logout button — hidden until logged in -->
             <button
@@ -484,8 +491,10 @@ try {
           const chk = document.getElementById('upload-keep-original');
           if (chk && user.store_originals_default) chk.checked = true;
 
-          // Admin: poll for active jobs and show a badge in the nav
+          // Admin: show admin link and poll for active jobs
           if (user.is_admin) {
+            const adminLink = document.getElementById('nav-admin');
+            if (adminLink) adminLink.style.display = '';
             const badge = document.getElementById('admin-jobs-badge');
             async function pollJobs() {
               try {
diff --git a/site/src/pages/admin/index.astro b/site/src/pages/admin/index.astro
new file mode 100644
index 0000000..89ab8bf
--- /dev/null
+++ b/site/src/pages/admin/index.astro
@@ -0,0 +1,93 @@
+---
+import Base from '../../layouts/Base.astro';
+---
+<Base title="Admin — BincioActivity">
+  <div class="max-w-2xl mx-auto px-4 py-10">
+    <h1 class="text-2xl font-bold text-white mb-8">Admin</h1>
+
+    <h2 class="text-sm font-semibold text-zinc-400 uppercase tracking-wider mb-3">Users</h2>
+    <div id="user-list" class="space-y-2">
+      <p class="text-zinc-500 text-sm">Loading…</p>
+    </div>
+
+    <!-- Confirmation dialog -->
+    <dialog id="confirm-dialog" class="rounded-xl bg-zinc-900 border border-zinc-700 p-6 text-white max-w-sm w-full backdrop:bg-black/60">
+      <p class="text-sm text-zinc-300 mb-5">Delete all activities for <strong id="confirm-handle" class="text-white"></strong>? This cannot be undone.</p>
+      <div class="flex gap-3 justify-end">
+        <button id="confirm-cancel" class="px-4 py-2 rounded-lg text-sm bg-zinc-800 hover:bg-zinc-700 text-zinc-300 transition-colors">Cancel</button>
+        <button id="confirm-ok" class="px-4 py-2 rounded-lg text-sm bg-red-700 hover:bg-red-600 text-white font-medium transition-colors">Delete</button>
+      </div>
+    </dialog>
+  </div>
+</Base>
+
+<script>
+  const listEl   = document.getElementById('user-list')!;
+  const dialog   = document.getElementById('confirm-dialog') as HTMLDialogElement;
+  const confirmH = document.getElementById('confirm-handle')!;
+  const confirmOk     = document.getElementById('confirm-ok')!;
+  const confirmCancel = document.getElementById('confirm-cancel')!;
+
+  let pendingHandle = '';
+
+  async function load() {
+    const r = await fetch('/api/admin/users', { credentials: 'include' });
+    if (!r.ok) {
+      listEl.innerHTML = '<p class="text-red-400 text-sm">Not authorised or server unavailable.</p>';
+      return;
+    }
+    const users = await r.json();
+    if (!users.length) {
+      listEl.innerHTML = '<p class="text-zinc-500 text-sm">No users.</p>';
+      return;
+    }
+    listEl.innerHTML = users.map((u: { handle: string; display_name: string; is_admin: boolean }) => `
+      <div class="flex items-center justify-between px-4 py-3 rounded-lg bg-zinc-900 border border-zinc-800" data-handle="${u.handle}">
+        <div>
+          <span class="text-sm font-medium text-white">@${u.handle}</span>
+          ${u.display_name ? `<span class="text-zinc-500 text-sm ml-2">${u.display_name}</span>` : ''}
+          ${u.is_admin ? '<span class="ml-2 text-xs text-amber-400">admin</span>' : ''}
+        </div>
+        <button
+          class="delete-btn text-xs px-3 py-1.5 rounded-lg bg-zinc-800 hover:bg-red-900 hover:text-red-300 text-zinc-400 transition-colors"
+          data-handle="${u.handle}"
+        >Delete activities</button>
+      </div>
+    `).join('');
+
+    listEl.querySelectorAll<HTMLButtonElement>('.delete-btn').forEach(btn => {
+      btn.addEventListener('click', () => {
+        pendingHandle = btn.dataset.handle!;
+        confirmH.textContent = pendingHandle;
+        dialog.showModal();
+      });
+    });
+  }
+
+  confirmCancel.addEventListener('click', () => dialog.close());
+  dialog.addEventListener('click', e => { if (e.target === dialog) dialog.close(); });
+
+  confirmOk.addEventListener('click', async () => {
+    dialog.close();
+    const row = listEl.querySelector(`[data-handle="${pendingHandle}"]`);
+    const btn = row?.querySelector<HTMLButtonElement>('.delete-btn');
+    if (btn) { btn.disabled = true; btn.textContent = 'Deleting…'; }
+
+    try {
+      const r = await fetch(`/api/admin/users/${pendingHandle}/activities`, {
+        method: 'DELETE',
+        credentials: 'include',
+      });
+      const d = await r.json();
+      if (r.ok) {
+        if (btn) { btn.textContent = `Deleted (${d.deleted})`; btn.classList.add('text-green-500'); }
+      } else {
+        if (btn) { btn.disabled = false; btn.textContent = 'Error: ' + (d.detail ?? 'failed'); btn.classList.add('text-red-400'); }
+      }
+    } catch (e: any) {
+      if (btn) { btn.disabled = false; btn.textContent = 'Error'; btn.classList.add('text-red-400'); }
+    }
+  });
+
+  load();
+</script>