diff --git a/src/app/router.tsx b/src/app/router.tsx
index 5b0c693..1bde52d 100644
--- a/src/app/router.tsx
+++ b/src/app/router.tsx
@@ -18,6 +18,7 @@ import { PresentationGenereeT1Page } from '@/features/simulations/pages/Presenta
 import { HistoriquePage } from '@/features/historique/pages/HistoriquePage'
 import { ProgressionPage } from '@/features/progression/pages/ProgressionPage'
 import { PricingPage } from '@/features/billing/pages/PricingPage'
+import { ParametresPage } from '@/features/account/pages/ParametresPage'
 import { SimulationFlowProvider } from '@/features/simulations/state/SimulationFlowProvider'
 import { AppLayout } from './AppLayout'
 
@@ -91,7 +92,7 @@ export function AppRouter() {
         <Route path="/methodologie" element={<ComingSoon />} />
         <Route path="/historique" element={<HistoriquePage />} />
         <Route path="/plan" element={<PricingPage />} />
-        <Route path="/parametres" element={<ComingSoon />} />
+        <Route path="/parametres" element={<ParametresPage />} />
       </Route>
 
       {/* ── Dev only ─────────────────────────────────────────────── */}
diff --git a/src/features/account/pages/ParametresPage.tsx b/src/features/account/pages/ParametresPage.tsx
new file mode 100644
index 0000000..4499239
--- /dev/null
+++ b/src/features/account/pages/ParametresPage.tsx
@@ -0,0 +1,67 @@
+/**
+ * Page Paramètres — Sprint 5d.
+ *
+ * Page minimale conteneur pour les sections de gestion du compte :
+ *   - Abonnement (`AccountBillingSection`) — Stripe.
+ *   - Session — bouton de déconnexion.
+ * Future : préférences langue, sécurité (changement mot de passe),
+ * suppression compte, etc.
+ *
+ * Wrapper layout standard 1100px (cohérent avec convention Sprint 4.7).
+ */
+
+import { useNavigate } from 'react-router-dom'
+import { useQueryClient } from '@tanstack/react-query'
+import { LogOut } from 'lucide-react'
+import { Button } from '@/shared/ui/Button'
+import { Card } from '@/shared/ui/Card'
+import { signOut } from '@/shared/lib/auth-client'
+import { AccountBillingSection } from '@/features/billing/components/AccountBillingSection'
+
+export function ParametresPage() {
+  const navigate = useNavigate()
+  const queryClient = useQueryClient()
+
+  async function handleSignOut() {
+    await signOut()
+    queryClient.clear()
+    navigate('/login', { replace: true })
+  }
+
+  return (
+    <div className="mx-auto w-full max-w-[1100px] px-5 py-6 lg:px-9 lg:py-9">
+      <header className="mb-8">
+        <p className="text-[11px] font-semibold uppercase tracking-[0.073em] text-ink-tertiary">
+          Paramètres
+        </p>
+        <h1 className="mt-1 text-[32px] font-bold tracking-[-0.02em] text-ink-primary">
+          Mon compte
+        </h1>
+        <p className="mt-2 text-sm text-ink-secondary">
+          Gérez votre abonnement, vos préférences et la sécurité de votre compte.
+        </p>
+      </header>
+
+      <div className="space-y-6">
+        <AccountBillingSection />
+
+        <Card variant="default" className="space-y-4 p-6">
+          <header>
+            <h2 className="text-lg font-semibold text-ink-primary">Session</h2>
+            <p className="mt-1 text-sm text-ink-secondary">
+              Terminer votre session sur cet appareil.
+            </p>
+          </header>
+          <Button
+            variant="secondary"
+            size="md"
+            icon={<LogOut className="size-4" aria-hidden="true" />}
+            onClick={handleSignOut}
+          >
+            Se déconnecter
+          </Button>
+        </Card>
+      </div>
+    </div>
+  )
+}
diff --git a/src/features/billing/__tests__/AccountBillingSection.test.tsx b/src/features/billing/__tests__/AccountBillingSection.test.tsx
new file mode 100644
index 0000000..c76b604
--- /dev/null
+++ b/src/features/billing/__tests__/AccountBillingSection.test.tsx
@@ -0,0 +1,99 @@
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { render, screen, cleanup } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { MemoryRouter } from 'react-router-dom'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+
+// ─── Mocks ───────────────────────────────────────────────────────────────────
+
+const { usePlanMock, useCustomerPortalMock } = vi.hoisted(() => ({
+  usePlanMock: vi.fn(),
+  useCustomerPortalMock: vi.fn(),
+}))
+
+vi.mock('@/features/dashboard/hooks/usePlan', () => ({
+  usePlan: usePlanMock,
+}))
+
+vi.mock('../hooks/useCustomerPortal', () => ({
+  useCustomerPortal: useCustomerPortalMock,
+}))
+
+import { AccountBillingSection } from '../components/AccountBillingSection'
+
+afterEach(() => {
+  cleanup()
+  usePlanMock.mockReset()
+  useCustomerPortalMock.mockReset()
+})
+
+function renderSection() {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false }, mutations: { retry: false } },
+  })
+  return render(
+    <QueryClientProvider client={queryClient}>
+      <MemoryRouter>
+        <AccountBillingSection />
+      </MemoryRouter>
+    </QueryClientProvider>,
+  )
+}
+
+function mockPlan(plan: 'free' | 'standard' | 'premium') {
+  usePlanMock.mockReturnValue({
+    data: { plan, permissions: {}, simulations_used: 0, simulations_remaining: null },
+    isLoading: false,
+  })
+}
+
+function mockPortal(overrides: Partial<ReturnType<typeof useCustomerPortalMock>> = {}) {
+  const openPortal = vi.fn()
+  useCustomerPortalMock.mockReturnValue({
+    openPortal,
+    isLoading: false,
+    error: null,
+    ...overrides,
+  })
+  return openPortal
+}
+
+// ─── Tests ───────────────────────────────────────────────────────────────────
+
+describe('AccountBillingSection — plan free', () => {
+  it('affiche le badge Découverte + lien "Voir les plans" → /plan', () => {
+    mockPlan('free')
+    mockPortal()
+    renderSection()
+
+    expect(screen.getByText('Plan Découverte')).toBeInTheDocument()
+    const link = screen.getByRole('link', { name: /voir les plans/i })
+    expect(link).toHaveAttribute('href', '/plan')
+    expect(screen.queryByRole('button', { name: /gérer mon abonnement/i })).not.toBeInTheDocument()
+  })
+})
+
+describe('AccountBillingSection — plan standard', () => {
+  it('clic sur "Gérer mon abonnement" appelle openPortal', async () => {
+    const user = userEvent.setup()
+    mockPlan('standard')
+    const openPortal = mockPortal()
+    renderSection()
+
+    expect(screen.getByText('Plan Standard')).toBeInTheDocument()
+    const btn = screen.getByRole('button', { name: /gérer mon abonnement/i })
+    expect(btn).toBeEnabled()
+
+    await user.click(btn)
+    expect(openPortal).toHaveBeenCalledTimes(1)
+    expect(screen.queryByRole('link', { name: /voir les plans/i })).not.toBeInTheDocument()
+  })
+
+  it("affiche un callout d'erreur quand le hook expose error", () => {
+    mockPlan('premium')
+    mockPortal({ error: 'Aucun abonnement actif trouvé.' })
+    renderSection()
+
+    expect(screen.getByRole('alert')).toHaveTextContent(/Aucun abonnement actif trouvé/i)
+  })
+})
diff --git a/src/features/billing/__tests__/PricingPage.test.tsx b/src/features/billing/__tests__/PricingPage.test.tsx
index 1f97047..fa076fc 100644
--- a/src/features/billing/__tests__/PricingPage.test.tsx
+++ b/src/features/billing/__tests__/PricingPage.test.tsx
@@ -6,10 +6,13 @@ import { MemoryRouter } from 'react-router-dom'
 
 // ─── Mocks ───────────────────────────────────────────────────────────────────
 
-const { usePlanMock, createCheckoutSessionMock } = vi.hoisted(() => ({
-  usePlanMock: vi.fn(),
-  createCheckoutSessionMock: vi.fn(),
-}))
+const { usePlanMock, createCheckoutSessionMock, createCustomerPortalSessionMock } = vi.hoisted(
+  () => ({
+    usePlanMock: vi.fn(),
+    createCheckoutSessionMock: vi.fn(),
+    createCustomerPortalSessionMock: vi.fn(),
+  }),
+)
 
 vi.mock('@/features/dashboard/hooks/usePlan', () => ({
   usePlan: usePlanMock,
@@ -17,6 +20,7 @@ vi.mock('@/features/dashboard/hooks/usePlan', () => ({
 
 vi.mock('../api', () => ({
   createCheckoutSession: createCheckoutSessionMock,
+  createCustomerPortalSession: createCustomerPortalSessionMock,
 }))
 
 import { PricingPage } from '../pages/PricingPage'
@@ -25,6 +29,7 @@ afterEach(() => {
   cleanup()
   usePlanMock.mockReset()
   createCheckoutSessionMock.mockReset()
+  createCustomerPortalSessionMock.mockReset()
 })
 
 function renderPage() {
@@ -120,6 +125,20 @@ describe('PricingPage — interaction', () => {
     expect(createCheckoutSessionMock.mock.calls[0]?.[0]).toBe('standard')
   })
 
+  it('Standard user clique "Passer en Premium" → createCustomerPortalSession (PAS createCheckoutSession)', async () => {
+    const user = userEvent.setup()
+    mockPlan('standard')
+    createCustomerPortalSessionMock.mockReturnValue(new Promise(() => {}))
+
+    renderPage()
+    await user.click(screen.getByRole('button', { name: /Passer en Premium$/ }))
+
+    await waitFor(() => {
+      expect(createCustomerPortalSessionMock).toHaveBeenCalledTimes(1)
+    })
+    expect(createCheckoutSessionMock).not.toHaveBeenCalled()
+  })
+
   it("erreur de mutation → callout d'erreur affiché", async () => {
     const user = userEvent.setup()
     mockPlan('free')
diff --git a/src/features/billing/__tests__/useCustomerPortal.test.tsx b/src/features/billing/__tests__/useCustomerPortal.test.tsx
new file mode 100644
index 0000000..4e510fd
--- /dev/null
+++ b/src/features/billing/__tests__/useCustomerPortal.test.tsx
@@ -0,0 +1,97 @@
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { renderHook, act, waitFor } from '@testing-library/react'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import type { ReactNode } from 'react'
+
+// ─── Mocks ───────────────────────────────────────────────────────────────────
+
+const { createCustomerPortalSessionMock } = vi.hoisted(() => ({
+  createCustomerPortalSessionMock: vi.fn(),
+}))
+
+vi.mock('../api', () => ({
+  createCustomerPortalSession: createCustomerPortalSessionMock,
+}))
+
+import { useCustomerPortal } from '../hooks/useCustomerPortal'
+
+afterEach(() => {
+  createCustomerPortalSessionMock.mockReset()
+})
+
+function wrapper({ children }: { children: ReactNode }) {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false }, mutations: { retry: false } },
+  })
+  return <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
+}
+
+// ─── Tests ───────────────────────────────────────────────────────────────────
+
+describe('useCustomerPortal', () => {
+  it("openPortal() succès → window.location.href set sur l'URL portal", async () => {
+    const originalLocation = window.location
+    const hrefSetter = vi.fn()
+    Object.defineProperty(window, 'location', {
+      configurable: true,
+      writable: true,
+      value: {
+        ...originalLocation,
+        get href() {
+          return originalLocation.href
+        },
+        set href(v: string) {
+          hrefSetter(v)
+        },
+      },
+    })
+
+    createCustomerPortalSessionMock.mockResolvedValue({
+      url: 'https://billing.stripe.com/p/session/abc',
+    })
+
+    const { result } = renderHook(() => useCustomerPortal(), { wrapper })
+    act(() => {
+      result.current.openPortal()
+    })
+
+    await waitFor(() => {
+      expect(hrefSetter).toHaveBeenCalledWith('https://billing.stripe.com/p/session/abc')
+    })
+
+    Object.defineProperty(window, 'location', {
+      configurable: true,
+      writable: true,
+      value: originalLocation,
+    })
+  })
+
+  it('erreur backend → message backend propagé dans `error`', async () => {
+    createCustomerPortalSessionMock.mockRejectedValue(
+      new Error('Aucun abonnement actif trouvé. Souscrivez d’abord à un plan.'),
+    )
+    const { result } = renderHook(() => useCustomerPortal(), { wrapper })
+
+    act(() => {
+      result.current.openPortal()
+    })
+
+    await waitFor(() => {
+      expect(result.current.error).toMatch(/Aucun abonnement actif trouvé/)
+    })
+  })
+
+  it('isLoading vrai pendant la mutation pending', async () => {
+    createCustomerPortalSessionMock.mockReturnValue(new Promise(() => {}))
+    const { result } = renderHook(() => useCustomerPortal(), { wrapper })
+
+    expect(result.current.isLoading).toBe(false)
+    act(() => {
+      result.current.openPortal()
+    })
+
+    await waitFor(() => {
+      expect(result.current.isLoading).toBe(true)
+    })
+  })
+})
diff --git a/src/features/billing/components/AccountBillingSection.tsx b/src/features/billing/components/AccountBillingSection.tsx
new file mode 100644
index 0000000..535d5f5
--- /dev/null
+++ b/src/features/billing/components/AccountBillingSection.tsx
@@ -0,0 +1,86 @@
+/**
+ * Sprint 5d — Section Abonnement de la page Paramètres.
+ *
+ * Affiche le plan actuel + un CTA contextuel :
+ *   - Plan free  → lien « Voir les plans » vers `/plan`.
+ *   - Plan payant → bouton « Gérer mon abonnement » → Stripe Customer Portal.
+ *
+ * Règle D : aucune comparaison `plan === 'xxx'` exposée hors d'un mapping
+ * explicite (ici la branche est binaire free vs payant).
+ * Règle L : tokens DA Charcoal exclusivement.
+ */
+
+import { Link } from 'react-router-dom'
+import { Button } from '@/shared/ui/Button'
+import { Card } from '@/shared/ui/Card'
+import { Badge } from '@/shared/ui/Badge'
+import { usePlan } from '@/features/dashboard/hooks/usePlan'
+import { useCustomerPortal } from '../hooks/useCustomerPortal'
+
+const PLAN_LABEL: Record<'free' | 'standard' | 'premium', string> = {
+  free: 'Plan Découverte',
+  standard: 'Plan Standard',
+  premium: 'Plan Premium',
+}
+
+export function AccountBillingSection() {
+  const { data: planData, isLoading: isPlanLoading } = usePlan()
+  const { openPortal, isLoading: isPortalLoading, error: portalError } = useCustomerPortal()
+
+  if (isPlanLoading || !planData) {
+    return (
+      <Card variant="default" className="p-6">
+        <div
+          className="h-24 animate-pulse rounded bg-surface-hover"
+          aria-busy="true"
+          aria-label="Chargement du plan…"
+        />
+      </Card>
+    )
+  }
+
+  const plan = planData.plan as 'free' | 'standard' | 'premium'
+  const isSubscribed = plan !== 'free'
+
+  return (
+    <Card variant="default" className="space-y-4 p-6">
+      <header className="flex flex-wrap items-center justify-between gap-3">
+        <h2 className="text-lg font-semibold text-ink-primary">Abonnement</h2>
+        <Badge variant="plan" planValue={plan}>
+          {PLAN_LABEL[plan]}
+        </Badge>
+      </header>
+
+      {isSubscribed ? (
+        <>
+          <p className="text-sm text-ink-secondary">
+            Modifier votre plan, mettre à jour votre moyen de paiement, ou consulter vos factures.
+          </p>
+          <Button variant="primary" size="md" onClick={openPortal} loading={isPortalLoading}>
+            Gérer mon abonnement
+          </Button>
+          {portalError && (
+            <p
+              role="alert"
+              className="rounded-md border border-danger/30 bg-danger-soft px-3 py-2 text-sm text-danger"
+            >
+              {portalError}
+            </p>
+          )}
+        </>
+      ) : (
+        <>
+          <p className="text-sm text-ink-secondary">
+            Vous utilisez actuellement le plan gratuit (5 simulations à vie). Découvrez les plans
+            payants pour un entraînement illimité avec correction détaillée.
+          </p>
+          <Button variant="primary" size="md">
+            <Link to="/plan" className="-m-1 p-1">
+              Voir les plans
+            </Link>
+          </Button>
+        </>
+      )}
+    </Card>
+  )
+}
diff --git a/src/features/billing/hooks/useCustomerPortal.ts b/src/features/billing/hooks/useCustomerPortal.ts
new file mode 100644
index 0000000..c04b6cf
--- /dev/null
+++ b/src/features/billing/hooks/useCustomerPortal.ts
@@ -0,0 +1,55 @@
+/**
+ * Sprint 5d — Hook Stripe Customer Portal.
+ *
+ * Wrap la mutation `createCustomerPortalSession` + redirect full-page vers
+ * la session Customer Portal Stripe. Utilisé par :
+ *   - `AccountBillingSection` (page Paramètres) : bouton « Gérer mon abonnement ».
+ *   - `PricingPage` (Standard→Premium) : redirige vers le portal qui gère
+ *     nativement l'upgrade prorata + confirmation du montant.
+ *
+ * Erreur 400 `NO_ACTIVE_SUBSCRIPTION` propagée telle quelle (le backend
+ * fournit déjà un message FR exploitable directement).
+ */
+
+import { useState } from 'react'
+import { useMutation } from '@tanstack/react-query'
+import { createCustomerPortalSession } from '../api'
+
+export interface UseCustomerPortalResult {
+  openPortal: () => void
+  isLoading: boolean
+  error: string | null
+}
+
+const FALLBACK_ERROR_MESSAGE =
+  'Impossible d’ouvrir l’espace abonnement. Réessayez dans quelques instants.'
+
+export function useCustomerPortal(): UseCustomerPortalResult {
+  const [error, setError] = useState<string | null>(null)
+
+  const mutation = useMutation({
+    mutationFn: createCustomerPortalSession,
+    onSuccess: (data) => {
+      // Redirect full-page : l'utilisateur reviendra sur ${APP_URL}/dashboard
+      // (cf. backend `return_url`). Le query param `?upgrade=success` n'est PAS
+      // ajouté par le portal — pas de banner de bienvenue dans ce flow,
+      // seulement une éventuelle invalidation au refresh manuel.
+      window.location.href = data.url
+    },
+    onError: (err: unknown) => {
+      const message = err instanceof Error && err.message ? err.message : FALLBACK_ERROR_MESSAGE
+      setError(message)
+    },
+  })
+
+  function openPortal(): void {
+    setError(null)
+    mutation.mutate()
+  }
+
+  return {
+    openPortal,
+    isLoading: mutation.isPending,
+    error,
+  }
+}
diff --git a/src/features/billing/pages/PricingPage.tsx b/src/features/billing/pages/PricingPage.tsx
index 973298a..326aadc 100644
--- a/src/features/billing/pages/PricingPage.tsx
+++ b/src/features/billing/pages/PricingPage.tsx
@@ -20,6 +20,7 @@ import { useState } from 'react'
 import { usePlan } from '@/features/dashboard/hooks/usePlan'
 import { type PriceType } from '../api'
 import { useStripeCheckout } from '../hooks/useStripeCheckout'
+import { useCustomerPortal } from '../hooks/useCustomerPortal'
 import { PlanCard, type PlanCardCta } from '../components/PlanCard'
 
 type Plan = 'free' | 'standard' | 'premium'
@@ -87,12 +88,11 @@ interface CtaConfigs {
 
 function buildCtaConfigs(
   plan: Plan,
-  pendingType: PriceType | null,
+  isStandardPending: boolean,
+  isPremiumPending: boolean,
   onUpgrade: (priceType: PriceType) => void,
 ): CtaConfigs {
-  const isStandardPending = pendingType === 'standard'
-  const isPremiumPending = pendingType === 'premium'
-  const anyPending = pendingType !== null
+  const anyPending = isStandardPending || isPremiumPending
 
   if (plan === 'free') {
     return {
@@ -148,21 +148,33 @@ function buildCtaConfigs(
 
 export function PricingPage() {
   const { data: planData, isLoading } = usePlan()
-  const { checkout, pendingPriceType, error } = useStripeCheckout()
-  // Mémorise le dernier priceType cliqué pour rattacher l'erreur globale du
-  // hook à la bonne carte. Sprint 5c — `useStripeCheckout` n'expose qu'un
-  // `error` global (l'utilisateur ne clique qu'un CTA à la fois).
+  const { checkout, pendingPriceType, error: checkoutError } = useStripeCheckout()
+  const { openPortal, isLoading: isPortalLoading, error: portalError } = useCustomerPortal()
+  // Mémorise le dernier priceType cliqué pour rattacher l'erreur (checkout OU
+  // portal) à la bonne carte. L'utilisateur ne clique qu'un CTA à la fois.
   const [lastClicked, setLastClicked] = useState<PriceType | null>(null)
 
+  const plan = (planData?.plan as Plan | undefined) ?? 'free'
+
+  // Sprint 5d — branche Standard→Premium via Customer Portal (Stripe affiche
+  // le montant prorata + confirmation native). Free→* reste sur Checkout direct.
   function handleUpgrade(priceType: PriceType) {
     setLastClicked(priceType)
-    checkout(priceType)
+    if (plan === 'standard') {
+      openPortal()
+    } else {
+      checkout(priceType)
+    }
   }
 
-  const plan = (planData?.plan as Plan | undefined) ?? 'free'
-  const ctaConfigs = buildCtaConfigs(plan, pendingPriceType, handleUpgrade)
+  // Loading par carte : combine la source pertinente selon le plan utilisateur.
+  const isStandardPending = pendingPriceType === 'standard'
+  const isPremiumPending = plan === 'standard' ? isPortalLoading : pendingPriceType === 'premium'
+
+  const ctaConfigs = buildCtaConfigs(plan, isStandardPending, isPremiumPending, handleUpgrade)
+  const effectiveError = checkoutError ?? portalError
   const errorByType: Partial<Record<PriceType, string>> =
-    error && lastClicked ? { [lastClicked]: error } : {}
+    effectiveError && lastClicked ? { [lastClicked]: effectiveError } : {}
 
   return (
     <div className="mx-auto w-full max-w-[1100px] px-5 py-6 lg:px-9 lg:py-9">