diff --git a/frontend/src/components/Icon.vue b/frontend/src/components/Icon.vue
index c2d6065..a30f409 100644
--- a/frontend/src/components/Icon.vue
+++ b/frontend/src/components/Icon.vue
@@ -20,6 +20,8 @@ const paths: Record<string, string> = {
   bell: '<path d="M10.268 21a2 2 0 0 0 3.464 0"/><path d="M3.262 15.326A1 1 0 0 0 4 17h16a1 1 0 0 0 .74-1.673C19.41 13.956 18 12.499 18 8A6 6 0 0 0 6 8c0 4.499-1.411 5.956-2.738 7.326"/>',
   grip: '<circle cx="9" cy="5" r="1" fill="currentColor"/><circle cx="9" cy="12" r="1" fill="currentColor"/><circle cx="9" cy="19" r="1" fill="currentColor"/><circle cx="15" cy="5" r="1" fill="currentColor"/><circle cx="15" cy="12" r="1" fill="currentColor"/><circle cx="15" cy="19" r="1" fill="currentColor"/>',
   calendar: '<path d="M8 2v4"/><path d="M16 2v4"/><rect width="18" height="18" x="3" y="4" rx="2"/><path d="M3 10h18"/>',
+  close: '<path d="M18 6 6 18"/><path d="m6 6 12 12"/>',
+  merge: '<circle cx="18" cy="18" r="3"/><circle cx="6" cy="6" r="3"/><path d="M6 21V9a9 9 0 0 0 9 9"/>',
 };
 </script>
 
diff --git a/frontend/src/components/LabelsModal.vue b/frontend/src/components/LabelsModal.vue
index 1233247..4f96c96 100644
--- a/frontend/src/components/LabelsModal.vue
+++ b/frontend/src/components/LabelsModal.vue
@@ -1,6 +1,6 @@
 <script setup lang="ts">
-import { ref } from "vue";
-import { useLabelsStore } from "../stores/labels";
+import { computed, ref } from "vue";
+import { useLabelsStore, type Label } from "../stores/labels";
 import { NOTE_COLOR_KEYS, NOTE_COLOR_LABELS, NOTE_SWATCH_CLASSES, type NoteColor } from "../notes/colors";
 import Icon from "./Icon.vue";
 
@@ -8,6 +8,9 @@ const emit = defineEmits<{ (e: "close"): void }>();
 const labels = useLabelsStore();
 const newName = ref("");
 const pickerFor = ref<string | null>(null);
+const mergeFor = ref<string | null>(null);
+
+const canMerge = computed(() => labels.items.length > 1);
 
 async function add() {
   const name = newName.value.trim();
@@ -25,10 +28,29 @@ function labelDot(color: string): string {
   return NOTE_SWATCH_CLASSES[color as NoteColor] ?? NOTE_SWATCH_CLASSES.default;
 }
 
+function openColor(id: string) {
+  mergeFor.value = null;
+  pickerFor.value = pickerFor.value === id ? null : id;
+}
+
 async function pickColor(id: string, color: NoteColor) {
   pickerFor.value = null;
   await labels.setColor(id, color);
 }
+
+function openMerge(id: string) {
+  pickerFor.value = null;
+  mergeFor.value = mergeFor.value === id ? null : id;
+}
+
+function otherLabels(id: string): Label[] {
+  return labels.items.filter((lb) => lb.id !== id);
+}
+
+async function doMerge(sourceId: string, targetId: string) {
+  mergeFor.value = null;
+  await labels.mergeInto(sourceId, targetId);
+}
 </script>
 
 <template>
@@ -43,7 +65,7 @@ async function pickColor(id: string, color: NoteColor) {
       @keydown.esc="emit('close')"
     >
       <div class="flex items-center justify-between border-b border-neutral-100 px-4 py-3 dark:border-neutral-800">
-        <h2 class="text-sm font-semibold">Edit labels</h2>
+        <h2 class="text-sm font-semibold">Manage labels</h2>
         <button type="button" class="icon-btn" aria-label="Close" @click="emit('close')"><Icon name="close" /></button>
       </div>
       <div class="flex flex-col gap-2 p-4">
@@ -57,20 +79,35 @@ async function pickColor(id: string, color: NoteColor) {
           />
         </form>
         <ul class="flex flex-col gap-1 pt-1">
-          <li v-for="lb in labels.items" :key="lb.id" class="relative flex items-center gap-2">
+          <li v-for="lb in labels.items" :key="lb.id" class="relative flex items-center gap-1.5">
             <button
               type="button"
               class="h-4 w-4 shrink-0 rounded-full border border-black/10 transition hover:scale-110 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand dark:border-white/15"
               :class="labelDot(lb.color)"
               :title="`Color: ${NOTE_COLOR_LABELS[(lb.color as NoteColor)] ?? lb.color}`"
               aria-label="Change label color"
-              @click="pickerFor = pickerFor === lb.id ? null : lb.id"
+              @click="openColor(lb.id)"
             />
             <input
               :value="lb.name"
-              class="flex-1 rounded-md bg-transparent px-2 py-1.5 text-sm outline-none focus-visible:ring-2 focus-visible:ring-brand"
+              class="min-w-0 flex-1 rounded-md bg-transparent px-2 py-1.5 text-sm outline-none focus-visible:ring-2 focus-visible:ring-brand"
               @change="rename(lb.id, ($event.target as HTMLInputElement).value)"
             />
+            <span
+              class="shrink-0 tabular-nums text-xs text-neutral-400"
+              :title="`${lb.count ?? 0} note${(lb.count ?? 0) === 1 ? '' : 's'}`"
+              >{{ lb.count ?? 0 }}</span
+            >
+            <button
+              v-if="canMerge"
+              type="button"
+              class="icon-btn"
+              title="Merge into another label"
+              aria-label="Merge into another label"
+              @click="openMerge(lb.id)"
+            >
+              <Icon name="merge" />
+            </button>
             <button
               type="button"
               class="icon-btn"
@@ -95,6 +132,29 @@ async function pickColor(id: string, color: NoteColor) {
                 @click="pickColor(lb.id, key)"
               />
             </div>
+            <div
+              v-if="mergeFor === lb.id"
+              class="absolute right-0 top-full z-10 mt-1 w-52 rounded-lg border border-neutral-200 bg-white p-1 shadow-lg dark:border-neutral-700 dark:bg-neutral-800"
+            >
+              <p class="px-2 py-1 text-xs text-neutral-400">
+                Merge “{{ lb.name }}” into… <span class="text-neutral-300 dark:text-neutral-500">(keeps notes)</span>
+              </p>
+              <ul class="max-h-44 overflow-y-auto">
+                <li v-for="t in otherLabels(lb.id)" :key="t.id">
+                  <button
+                    type="button"
+                    class="flex w-full items-center gap-2 rounded-md px-2 py-1.5 text-left text-sm hover:bg-neutral-100 dark:hover:bg-neutral-700"
+                    @click="doMerge(lb.id, t.id)"
+                  >
+                    <span
+                      class="h-2.5 w-2.5 shrink-0 rounded-full border border-black/10 dark:border-white/15"
+                      :class="labelDot(t.color)"
+                    ></span>
+                    <span class="truncate">{{ t.name }}</span>
+                  </button>
+                </li>
+              </ul>
+            </div>
           </li>
         </ul>
         <p v-if="!labels.items.length" class="py-2 text-center text-xs text-neutral-400">
diff --git a/frontend/src/stores/labels.ts b/frontend/src/stores/labels.ts
index d08e2db..0e09a5a 100644
--- a/frontend/src/stores/labels.ts
+++ b/frontend/src/stores/labels.ts
@@ -6,6 +6,8 @@ export interface Label {
   id: string;
   name: string;
   color: string;
+  // Number of notes carrying this label (from GET /api/labels; used in label management).
+  count?: number;
 }
 
 export const useLabelsStore = defineStore("labels", () => {
@@ -34,14 +36,15 @@ export const useLabelsStore = defineStore("labels", () => {
   async function rename(id: string, name: string): Promise<void> {
     const updated = await api.patch<Label>(`/api/labels/${id}`, { name });
     const idx = items.value.findIndex((lb) => lb.id === id);
-    if (idx >= 0) items.value[idx] = updated;
+    // The single-label PATCH doesn't recompute the count — keep the one we have.
+    if (idx >= 0) items.value[idx] = { ...updated, count: items.value[idx].count };
     sort();
   }
 
   async function setColor(id: string, color: string): Promise<void> {
     const updated = await api.patch<Label>(`/api/labels/${id}`, { color });
     const idx = items.value.findIndex((lb) => lb.id === id);
-    if (idx >= 0) items.value[idx] = updated;
+    if (idx >= 0) items.value[idx] = { ...updated, count: items.value[idx].count };
   }
 
   async function remove(id: string): Promise<void> {
@@ -49,5 +52,15 @@ export const useLabelsStore = defineStore("labels", () => {
     items.value = items.value.filter((lb) => lb.id !== id);
   }
 
-  return { items, loaded, load, create, rename, setColor, remove };
+  // Merge `sourceId` into `targetId`: the server moves the source's notes onto the
+  // target and deletes the source; the response carries the target's new count.
+  async function mergeInto(sourceId: string, targetId: string): Promise<void> {
+    const target = await api.post<Label>(`/api/labels/${sourceId}/merge`, { into: targetId });
+    items.value = items.value.filter((lb) => lb.id !== sourceId);
+    const idx = items.value.findIndex((lb) => lb.id === targetId);
+    if (idx >= 0) items.value[idx] = target;
+    sort();
+  }
+
+  return { items, loaded, load, create, rename, setColor, remove, mergeInto };
 });
diff --git a/src/thoughtsync/labels.py b/src/thoughtsync/labels.py
index bff83b6..5a7e6d8 100644
--- a/src/thoughtsync/labels.py
+++ b/src/thoughtsync/labels.py
@@ -3,11 +3,11 @@ from __future__ import annotations
 import uuid
 
 from quart import Blueprint, g, jsonify, request
-from sqlalchemy import select
+from sqlalchemy import func, select
 
 from .auth import login_required
 from .db import session_scope
-from .models.label import Label
+from .models.label import Label, NoteLabel
 
 bp = Blueprint("labels", __name__, url_prefix="/api/labels")
 
@@ -19,8 +19,18 @@ def _normalize_label_color(color: object) -> str:
     return color if color in LABEL_COLORS else "default"
 
 
-def _serialize_label(label: Label) -> dict:
-    return {"id": str(label.id), "name": label.name, "color": label.color}
+def _serialize_label(label: Label, count: int | None = None) -> dict:
+    data = {"id": str(label.id), "name": label.name, "color": label.color}
+    if count is not None:
+        data["count"] = count
+    return data
+
+
+async def _label_note_count(db, label_id) -> int:
+    """How many notes carry this label (distinct — note_labels PK is note+label)."""
+    return int(
+        await db.scalar(select(func.count()).select_from(NoteLabel).where(NoteLabel.label_id == label_id)) or 0
+    )
 
 
 async def _get_owned_label(db, label_id: str) -> Label | None:
@@ -36,7 +46,17 @@ async def _get_owned_label(db, label_id: str) -> Label | None:
 async def list_labels():
     async with session_scope() as db:
         labels = (await db.scalars(select(Label).where(Label.owner_id == g.user_id).order_by(Label.name))).all()
-        return jsonify({"labels": [_serialize_label(lb) for lb in labels]})
+        # One grouped query for all usage counts (0 for labels attached to nothing).
+        counts = dict(
+            (
+                await db.execute(
+                    select(NoteLabel.label_id, func.count(NoteLabel.note_id))
+                    .where(NoteLabel.label_id.in_([lb.id for lb in labels]))
+                    .group_by(NoteLabel.label_id)
+                )
+            ).all()
+        ) if labels else {}
+        return jsonify({"labels": [_serialize_label(lb, int(counts.get(lb.id, 0))) for lb in labels]})
 
 
 @bp.post("")
@@ -55,7 +75,7 @@ async def create_label():
         db.add(label)
         await db.commit()
         await db.refresh(label)
-        return jsonify(_serialize_label(label)), 201
+        return jsonify(_serialize_label(label, 0)), 201
 
 
 @bp.patch("/<label_id>")
@@ -97,3 +117,42 @@ async def delete_label(label_id: str):
         await db.delete(label)  # note_labels rows cascade
         await db.commit()
         return jsonify({"ok": True})
+
+
+@bp.post("/<label_id>/merge")
+@login_required
+async def merge_label(label_id: str):
+    """Merge `label_id` (source) INTO the label given by body {"into": <id>}: move
+    every note tagged with the source onto the target, then delete the source. Both
+    must be owned by the caller. Note-body `#tags` are NOT rewritten, so a note whose
+    body still literally contains the source #tag will re-mint that label on its next
+    edit — retire a tag by editing it out of the text (a known, documented nuance)."""
+    data = await request.get_json(silent=True) or {}
+    into = data.get("into")
+    async with session_scope() as db:
+        source = await _get_owned_label(db, label_id)
+        target = await _get_owned_label(db, str(into)) if into is not None else None
+        if source is None or target is None:
+            return jsonify({"error": "not found"}), 404
+        if source.id == target.id:
+            return jsonify({"error": "cannot merge a label into itself"}), 400
+        # Notes already carrying the target: a note can't hold the same label twice
+        # (composite PK), so the source attachment there is just dropped as a dup.
+        target_notes = set(
+            (await db.scalars(select(NoteLabel.note_id).where(NoteLabel.label_id == target.id))).all()
+        )
+        source_rows = (await db.scalars(select(NoteLabel).where(NoteLabel.label_id == source.id))).all()
+        by_note = {r.note_id: r.via_tag for r in source_rows}
+        # Delete the source attachments first, then re-insert under the target — moving
+        # by delete+insert avoids mutating a composite primary-key column in place.
+        for row in source_rows:
+            await db.delete(row)
+        await db.flush()
+        for note_id, via_tag in by_note.items():
+            if note_id not in target_notes:
+                db.add(NoteLabel(note_id=note_id, label_id=target.id, via_tag=via_tag))
+        await db.delete(source)
+        await db.flush()
+        count = await _label_note_count(db, target.id)
+        await db.commit()
+        return jsonify(_serialize_label(target, count))
diff --git a/tests/test_labels.py b/tests/test_labels.py
index 7ccc43d..fa52856 100644
--- a/tests/test_labels.py
+++ b/tests/test_labels.py
@@ -21,3 +21,12 @@ async def test_set_note_labels_requires_auth(app):
         json={"label_ids": []},
     )
     assert resp.status_code == 401
+
+
+async def test_merge_label_requires_auth(app):
+    client = app.test_client()
+    resp = await client.post(
+        "/api/labels/00000000-0000-0000-0000-000000000000/merge",
+        json={"into": "00000000-0000-0000-0000-000000000001"},
+    )
+    assert resp.status_code == 401