diff --git a/frontend/src/pages/admin/AdminCategoriesPage.vue b/frontend/src/pages/admin/AdminCategoriesPage.vue
index ba39258..d3aa16e 100644
--- a/frontend/src/pages/admin/AdminCategoriesPage.vue
+++ b/frontend/src/pages/admin/AdminCategoriesPage.vue
@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { ref, onMounted } from 'vue'
+import { RouterLink } from 'vue-router'
 import { api, ApiError } from '@/api/client'
 import type { Category, Stats, Wrapped } from '@/types/api'
 import AdminSubNav from '@/components/AdminSubNav.vue'
@@ -94,13 +95,19 @@ async function destroy(c: Category) {
             <td class="px-4 py-3 text-right tabular-nums">{{ c.sort_order }}</td>
             <td class="px-4 py-3 text-right tabular-nums">{{ counts[c.slug] ?? 0 }}</td>
             <td class="px-4 py-3 text-right">
-              <button
-                type="button"
-                class="text-red-500 hover:text-red-700 text-xs font-medium disabled:opacity-30"
-                :disabled="(counts[c.slug] ?? 0) > 0"
-                :title="(counts[c.slug] ?? 0) > 0 ? 'Catégorie utilisée par des projets' : 'Supprimer'"
-                @click="destroy(c)"
-              >Supprimer</button>
+              <div class="inline-flex items-center gap-3">
+                <RouterLink
+                  :to="{ name: 'admin-category-edit', params: { slug: c.slug } }"
+                  class="text-donut-text hover:underline text-xs font-medium"
+                >Éditer</RouterLink>
+                <button
+                  type="button"
+                  class="text-red-500 hover:text-red-700 text-xs font-medium disabled:opacity-30"
+                  :disabled="(counts[c.slug] ?? 0) > 0"
+                  :title="(counts[c.slug] ?? 0) > 0 ? 'Catégorie utilisée par des projets' : 'Supprimer'"
+                  @click="destroy(c)"
+                >Supprimer</button>
+              </div>
             </td>
           </tr>
         </tbody>
diff --git a/frontend/src/pages/admin/AdminCategoryEditPage.vue b/frontend/src/pages/admin/AdminCategoryEditPage.vue
new file mode 100644
index 0000000..a602871
--- /dev/null
+++ b/frontend/src/pages/admin/AdminCategoryEditPage.vue
@@ -0,0 +1,298 @@
+<script setup lang="ts">
+import { ref, computed, onMounted } from 'vue'
+import { RouterLink, useRouter } from 'vue-router'
+import { api, ApiError } from '@/api/client'
+import { useAuth } from '@/composables/useAuth'
+import type { Category, Dimension } from '@/types/api'
+import AdminSubNav from '@/components/AdminSubNav.vue'
+import LoadingState from '@/components/LoadingState.vue'
+import ErrorState from '@/components/ErrorState.vue'
+
+const props = defineProps<{ slug: string }>()
+const router = useRouter()
+const { isAuthenticated } = useAuth()
+
+const category = ref<Category | null>(null)
+const loading = ref(true)
+const loadError = ref<string | null>(null)
+
+const form = ref({
+  name: '',
+  slug: '',
+  description: '',
+  color_hex: '#888888',
+  icon: '',
+  dimension: 'transversal' as Dimension,
+  sort_order: 0,
+})
+const submitting = ref(false)
+const fieldErrors = ref<Record<string, string>>({})
+const generalError = ref<string | null>(null)
+const justSaved = ref(false)
+
+async function load() {
+  loading.value = true
+  loadError.value = null
+  try {
+    const c = await api.get<Category>(`/api/categories/${encodeURIComponent(props.slug)}`)
+    category.value = c
+    form.value = {
+      name:        c.name,
+      slug:        c.slug,
+      description: c.description ?? '',
+      color_hex:   c.color_hex,
+      icon:        c.icon ?? '',
+      dimension:   c.dimension,
+      sort_order:  c.sort_order,
+    }
+  } catch (e) {
+    loadError.value = e instanceof ApiError ? (e.payload.message ?? e.code) : 'Erreur réseau'
+  } finally {
+    loading.value = false
+  }
+}
+onMounted(load)
+
+const slugChanged = computed(() => category.value !== null && form.value.slug !== category.value.slug)
+
+// `projects_count` est rempli par GET /api/categories/:slug (cf. controller PHP).
+const projectsCount = computed(() => category.value?.projects_count ?? 0)
+
+// Validation HEX côté client pour feedback immédiat (le serveur revalide).
+const colorValid = computed(() => /^#[0-9A-Fa-f]{6}$/.test(form.value.color_hex))
+
+const DIMENSION_OPTIONS: Array<{ value: Dimension; label: string; color: string }> = [
+  { value: 'social',      label: 'Plancher social',    color: '#F97316' },
+  { value: 'ecologique',  label: 'Plafond écologique', color: '#22C55E' },
+  { value: 'transversal', label: 'Transversal',        color: '#6B7280' },
+]
+
+async function submit() {
+  fieldErrors.value = {}
+  generalError.value = null
+  justSaved.value = false
+  if (!isAuthenticated.value) {
+    generalError.value = "Tu dois être connecté en admin."
+    return
+  }
+  if (!category.value) return
+  if (!colorValid.value) {
+    fieldErrors.value.color_hex = 'invalid_color_hex'
+    return
+  }
+
+  submitting.value = true
+  try {
+    const diff: Record<string, unknown> = {}
+    const c = category.value
+    if (form.value.name.trim() !== c.name)                 diff.name = form.value.name.trim()
+    if (slugChanged.value)                                 diff.slug = form.value.slug.trim()
+    if (form.value.description !== (c.description ?? '')) diff.description = form.value.description || null
+    if (form.value.color_hex.toUpperCase() !== c.color_hex.toUpperCase()) diff.color_hex = form.value.color_hex.toUpperCase()
+    if (form.value.icon !== (c.icon ?? ''))               diff.icon = form.value.icon || null
+    if (form.value.dimension !== c.dimension)             diff.dimension = form.value.dimension
+    if (form.value.sort_order !== c.sort_order)           diff.sort_order = form.value.sort_order
+
+    if (Object.keys(diff).length === 0) {
+      generalError.value = 'Aucune modification à enregistrer.'
+      submitting.value = false
+      return
+    }
+
+    const updated = await api.patch<Category>(`/api/categories/${encodeURIComponent(c.slug)}`, diff)
+    category.value = updated
+    if (updated.slug !== props.slug) {
+      router.replace({ name: 'admin-category-edit', params: { slug: updated.slug } })
+    }
+    justSaved.value = true
+  } catch (e) {
+    if (e instanceof ApiError) {
+      if (e.status === 422)         fieldErrors.value = e.fields
+      else if (e.status === 401)    generalError.value = 'Session admin expirée. Reconnecte-toi.'
+      else if (e.status === 409)    generalError.value = e.payload.message ?? 'Conflit (slug déjà pris ?)'
+      else                          generalError.value = e.payload.message ?? e.code
+    } else {
+      generalError.value = 'Erreur réseau'
+    }
+  } finally {
+    submitting.value = false
+  }
+}
+
+async function destroy() {
+  if (!category.value) return
+  if (projectsCount.value > 0) {
+    alert(`Impossible : ${projectsCount.value} projet(s) utilise(nt) cette catégorie.\nDéplace-les ou archive-les d'abord.`)
+    return
+  }
+  if (!confirm(`Supprimer définitivement « ${category.value.name} » ?`)) return
+  try {
+    await api.delete(`/api/categories/${encodeURIComponent(category.value.slug)}`)
+    router.push({ name: 'admin-categories' })
+  } catch (e) {
+    if (e instanceof ApiError) generalError.value = e.payload.message ?? e.code
+    else generalError.value = 'Erreur réseau'
+  }
+}
+</script>
+
+<template>
+  <section class="px-10 py-8 max-w-4xl">
+    <header class="mb-6">
+      <h1 class="text-3xl font-semibold text-donut-text">Administration</h1>
+      <p class="text-donut-muted mt-1">Édition d'une catégorie thématique.</p>
+    </header>
+    <AdminSubNav />
+
+    <LoadingState v-if="loading" class="mt-8" />
+    <ErrorState v-else-if="loadError" :message="loadError" :retry="load" class="mt-8" />
+
+    <div v-else-if="category" class="mt-6 space-y-4">
+      <RouterLink :to="{ name: 'admin-categories' }" class="inline-flex items-center gap-1.5 text-sm text-donut-muted hover:text-donut-text">
+        <svg viewBox="0 0 24 24" class="w-4 h-4" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+          <path d="m12 19-7-7 7-7M5 12h14"/>
+        </svg>
+        Retour aux catégories
+      </RouterLink>
+
+      <!-- Preview en haut : carte de catégorie comme rendue dans /categories -->
+      <div
+        class="rounded-xl border border-donut-border bg-donut-surface overflow-hidden"
+        :style="{ borderTopWidth: '4px', borderTopStyle: 'solid', borderTopColor: colorValid ? form.color_hex : '#D1D5DB' }"
+      >
+        <div class="p-5 flex items-start gap-4">
+          <div
+            class="w-11 h-11 rounded-lg flex items-center justify-center shrink-0"
+            :style="{ background: (colorValid ? form.color_hex : '#888888') + '1A', color: colorValid ? form.color_hex : '#6B7280' }"
+          >
+            <svg viewBox="0 0 24 24" class="w-5 h-5" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+              <path d="M3 7a2 2 0 0 1 2-2h4l2 2h8a2 2 0 0 1 2 2v9a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2z" />
+            </svg>
+          </div>
+          <div class="flex-1 min-w-0">
+            <h3 class="text-lg font-semibold text-donut-text">{{ form.name || '(sans nom)' }}</h3>
+            <p v-if="form.description" class="text-sm text-donut-muted mt-1">{{ form.description }}</p>
+            <div class="mt-3 flex items-center justify-between gap-2">
+              <span class="inline-flex items-center rounded-full bg-orange-50 text-status-active px-2.5 py-1 text-xs font-medium">
+                {{ projectsCount }} projet{{ projectsCount > 1 ? 's' : '' }}
+              </span>
+              <span class="text-[10px] text-donut-muted uppercase tracking-wider">
+                {{ DIMENSION_OPTIONS.find(d => d.value === form.dimension)?.label }}
+              </span>
+            </div>
+          </div>
+          <button
+            type="button"
+            class="text-xs font-medium text-red-500 hover:text-red-700 self-start"
+            :disabled="projectsCount > 0"
+            :title="projectsCount > 0 ? 'Catégorie utilisée par des projets' : 'Supprimer'"
+            @click="destroy"
+          >Supprimer</button>
+        </div>
+      </div>
+
+      <form @submit.prevent="submit" class="rounded-xl border border-donut-border bg-donut-surface p-6 space-y-5">
+        <div>
+          <label class="block text-sm font-medium text-donut-text mb-1">Nom *</label>
+          <input
+            v-model="form.name" type="text" maxlength="128"
+            class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text"
+            :class="fieldErrors.name ? 'border-red-400' : ''"
+          />
+          <p v-if="fieldErrors.name" class="text-xs text-red-600 mt-1">Nom requis.</p>
+        </div>
+
+        <div class="grid grid-cols-1 sm:grid-cols-[1fr,140px] gap-4">
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Slug</label>
+            <input
+              v-model="form.slug" type="text" maxlength="64"
+              class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm font-mono outline-none focus:border-donut-text"
+              :class="fieldErrors.slug ? 'border-red-400' : ''"
+            />
+            <p class="text-xs text-donut-muted mt-1">Identifiant URL. Casse les filtres existants.</p>
+          </div>
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Ordre</label>
+            <input
+              v-model.number="form.sort_order" type="number" min="0"
+              class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text"
+            />
+            <p class="text-xs text-donut-muted mt-1">Tri (asc).</p>
+          </div>
+        </div>
+
+        <div>
+          <label class="block text-sm font-medium text-donut-text mb-1">Description</label>
+          <textarea
+            v-model="form.description" rows="3" maxlength="5000"
+            class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text resize-y"
+          />
+        </div>
+
+        <div class="grid grid-cols-1 sm:grid-cols-2 gap-4">
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Couleur</label>
+            <div class="flex items-center gap-2">
+              <input
+                v-model="form.color_hex" type="color"
+                class="h-10 w-12 rounded border border-donut-border cursor-pointer"
+              />
+              <input
+                v-model="form.color_hex" type="text" maxlength="7" placeholder="#RRGGBB"
+                class="flex-1 bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm font-mono uppercase outline-none focus:border-donut-text"
+                :class="fieldErrors.color_hex || !colorValid ? 'border-red-400' : ''"
+              />
+            </div>
+            <p v-if="!colorValid" class="text-xs text-red-600 mt-1">Format attendu : #RRGGBB</p>
+          </div>
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Dimension Donut</label>
+            <select
+              v-model="form.dimension"
+              class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text"
+            >
+              <option v-for="d in DIMENSION_OPTIONS" :key="d.value" :value="d.value">{{ d.label }}</option>
+            </select>
+            <p class="text-xs text-donut-muted mt-1">
+              Détermine où les projets de cette catégorie se placent dans la viz Donut.
+            </p>
+          </div>
+        </div>
+
+        <div>
+          <label class="block text-sm font-medium text-donut-text mb-1">Icône (nom)</label>
+          <input
+            v-model="form.icon" type="text" maxlength="32"
+            placeholder="database / users / home / map / leaf / graduation-cap…"
+            class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm font-mono outline-none focus:border-donut-text"
+          />
+          <p class="text-xs text-donut-muted mt-1">
+            Nom d'icône (style Lucide). Champ libre — le rendu visuel sera ajouté ultérieurement.
+          </p>
+        </div>
+
+        <div v-if="generalError" class="rounded-lg border border-red-200 bg-red-50 text-red-700 px-3 py-2 text-sm">
+          {{ generalError }}
+        </div>
+        <div v-if="justSaved" class="rounded-lg border border-green-200 bg-green-50 text-green-700 px-3 py-2 text-sm">
+          Modifications enregistrées.
+        </div>
+
+        <div class="flex items-center justify-end gap-2 pt-2 border-t border-donut-border">
+          <RouterLink
+            :to="{ name: 'admin-categories' }"
+            class="px-4 py-2 rounded-lg text-sm font-medium border border-donut-border hover:bg-gray-50"
+          >Annuler</RouterLink>
+          <button
+            type="submit"
+            :disabled="submitting"
+            class="px-4 py-2 rounded-lg bg-donut-text text-white text-sm font-medium hover:bg-black disabled:opacity-50"
+          >
+            {{ submitting ? 'Enregistrement…' : 'Enregistrer' }}
+          </button>
+        </div>
+      </form>
+    </div>
+  </section>
+</template>
diff --git a/frontend/src/router/index.ts b/frontend/src/router/index.ts
index 0288a1e..268430b 100644
--- a/frontend/src/router/index.ts
+++ b/frontend/src/router/index.ts
@@ -40,6 +40,7 @@ const routes: RouteRecordRaw[] = [
       { path: 'admin/members', name: 'admin-members', component: () => import('@/pages/admin/AdminMembersPage.vue'), beforeEnter: requireAdmin },
       { path: 'admin/members/:slug/edit', name: 'admin-member-edit', component: () => import('@/pages/admin/AdminMemberEditPage.vue'), props: true, beforeEnter: requireAdmin },
       { path: 'admin/categories', name: 'admin-categories', component: () => import('@/pages/admin/AdminCategoriesPage.vue'), beforeEnter: requireAdmin },
+      { path: 'admin/categories/:slug/edit', name: 'admin-category-edit', component: () => import('@/pages/admin/AdminCategoryEditPage.vue'), props: true, beforeEnter: requireAdmin },
 
       { path: 'admin/login', name: 'admin-login', component: () => import('@/pages/AdminLoginPage.vue'), meta: { hideForAuthed: true } },
       { path: ':pathMatch(.*)*', name: 'not-found', component: () => import('@/pages/NotFoundPage.vue') },