diff --git a/apps/web/src/app/(portal)/settings/layout.tsx b/apps/web/src/app/(portal)/settings/layout.tsx
new file mode 100644
index 0000000..37fd430
--- /dev/null
+++ b/apps/web/src/app/(portal)/settings/layout.tsx
@@ -0,0 +1,47 @@
+'use client';
+
+import Link from 'next/link';
+import { useTranslations } from 'next-intl';
+import { SettingsSidebar } from '@/components/settings/settings-sidebar';
+
+/**
+ * Settings nested layout (D-19, D-20).
+ * Renders within the portal AppShell, adding its own sub-sidebar on the left.
+ * Back-to-dashboard link at top of content area per UI-SPEC.
+ */
+export default function SettingsLayout({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  const t = useTranslations('settings');
+
+  return (
+    <div className="flex h-full">
+      <SettingsSidebar />
+      <div className="flex-1 overflow-y-auto p-6">
+        {/* Back to Dashboard link */}
+        <Link
+          href="/"
+          className="mb-4 inline-flex items-center gap-1 text-sm text-muted-foreground transition-colors hover:text-foreground"
+        >
+          <svg
+            xmlns="http://www.w3.org/2000/svg"
+            width="16"
+            height="16"
+            viewBox="0 0 24 24"
+            fill="none"
+            stroke="currentColor"
+            strokeWidth="2"
+            strokeLinecap="round"
+            strokeLinejoin="round"
+          >
+            <polyline points="15 18 9 12 15 6" />
+          </svg>
+          {t('backToDashboard')}
+        </Link>
+        {children}
+      </div>
+    </div>
+  );
+}
diff --git a/apps/web/src/app/(portal)/settings/page.tsx b/apps/web/src/app/(portal)/settings/page.tsx
new file mode 100644
index 0000000..e820358
--- /dev/null
+++ b/apps/web/src/app/(portal)/settings/page.tsx
@@ -0,0 +1,8 @@
+import { redirect } from 'next/navigation';
+
+/**
+ * Settings index page — redirects to /settings/dashboard (the default category).
+ */
+export default function SettingsPage() {
+  redirect('/settings/dashboard');
+}
diff --git a/apps/web/src/components/layout/header.tsx b/apps/web/src/components/layout/header.tsx
index 1267158..878bd99 100644
--- a/apps/web/src/components/layout/header.tsx
+++ b/apps/web/src/components/layout/header.tsx
@@ -1,6 +1,7 @@
 'use client';
 
 import { useEffect, useRef, useState } from 'react';
+import Link from 'next/link';
 import { useTranslations } from 'next-intl';
 import { useSidebarStore } from '@/lib/stores/sidebar-store';
 import { useAuthStore } from '@/lib/stores/auth-store';
@@ -128,6 +129,31 @@ export function Header() {
                 )}
               </div>
 
+              {/* Settings link */}
+              <div className="px-2 py-1">
+                <Link
+                  href="/settings"
+                  onClick={() => setDropdownOpen(false)}
+                  className="flex w-full items-center gap-2 rounded-md px-2 py-1.5 text-sm text-foreground hover:bg-muted transition-colors"
+                >
+                  <svg
+                    xmlns="http://www.w3.org/2000/svg"
+                    width="16"
+                    height="16"
+                    viewBox="0 0 24 24"
+                    fill="none"
+                    stroke="currentColor"
+                    strokeWidth="2"
+                    strokeLinecap="round"
+                    strokeLinejoin="round"
+                  >
+                    <circle cx="12" cy="12" r="3" />
+                    <path d="M19.4 15a1.65 1.65 0 0 0 .33 1.82l.06.06a2 2 0 0 1 0 2.83 2 2 0 0 1-2.83 0l-.06-.06a1.65 1.65 0 0 0-1.82-.33 1.65 1.65 0 0 0-1 1.51V21a2 2 0 0 1-2 2 2 2 0 0 1-2-2v-.09A1.65 1.65 0 0 0 9 19.4a1.65 1.65 0 0 0-1.82.33l-.06.06a2 2 0 0 1-2.83 0 2 2 0 0 1 0-2.83l.06-.06A1.65 1.65 0 0 0 4.68 15a1.65 1.65 0 0 0-1.51-1H3a2 2 0 0 1-2-2 2 2 0 0 1 2-2h.09A1.65 1.65 0 0 0 4.6 9a1.65 1.65 0 0 0-.33-1.82l-.06-.06a2 2 0 0 1 0-2.83 2 2 0 0 1 2.83 0l.06.06A1.65 1.65 0 0 0 9 4.68a1.65 1.65 0 0 0 1-1.51V3a2 2 0 0 1 2-2 2 2 0 0 1 2 2v.09a1.65 1.65 0 0 0 1 1.51 1.65 1.65 0 0 0 1.82-.33l.06-.06a2 2 0 0 1 2.83 0 2 2 0 0 1 0 2.83l-.06.06A1.65 1.65 0 0 0 19.4 9a1.65 1.65 0 0 0 1.51 1H21a2 2 0 0 1 2 2 2 2 0 0 1-2 2h-.09a1.65 1.65 0 0 0-1.51 1z" />
+                  </svg>
+                  {tHeader('settings')}
+                </Link>
+              </div>
+
               {/* Logout button */}
               <div className="px-2 py-1">
                 <button
diff --git a/apps/web/src/components/settings/settings-sidebar.tsx b/apps/web/src/components/settings/settings-sidebar.tsx
new file mode 100644
index 0000000..5f3d16e
--- /dev/null
+++ b/apps/web/src/components/settings/settings-sidebar.tsx
@@ -0,0 +1,64 @@
+'use client';
+
+import Link from 'next/link';
+import { usePathname } from 'next/navigation';
+import { useTranslations } from 'next-intl';
+
+/**
+ * Settings sub-sidebar (D-19, D-20).
+ * Phase 05 categories: Dashboard > Widgets, Calendar.
+ * Active item uses sidebar-accent pattern with aria-current="page".
+ */
+export function SettingsSidebar() {
+  const t = useTranslations('settings');
+  const pathname = usePathname();
+
+  const items = [
+    {
+      label: t('categoryWidgets'),
+      href: '/settings/dashboard',
+    },
+    {
+      label: t('categoryCalendar'),
+      href: '/settings/dashboard/calendar',
+    },
+  ];
+
+  const isActive = (href: string) => {
+    if (href === '/settings/dashboard') {
+      // Active when exactly on /settings/dashboard (not on sub-routes like /calendar)
+      return pathname === '/settings/dashboard';
+    }
+    return pathname.startsWith(href);
+  };
+
+  return (
+    <aside
+      className="flex w-[220px] shrink-0 flex-col border-r border-sidebar-border bg-sidebar"
+      role="navigation"
+      aria-label={t('navLabel')}
+    >
+      <div className="p-4">
+        <h2 className="text-xs font-semibold uppercase tracking-wider text-muted-foreground">
+          {t('categoryDashboard')}
+        </h2>
+      </div>
+      <nav className="flex flex-col gap-1 px-3">
+        {items.map((item) => (
+          <Link
+            key={item.href}
+            href={item.href}
+            className={`flex items-center rounded-md px-2 py-1.5 text-sm transition-colors ${
+              isActive(item.href)
+                ? 'bg-sidebar-accent text-sidebar-accent-foreground font-medium'
+                : 'text-sidebar-foreground hover:bg-muted'
+            }`}
+            aria-current={isActive(item.href) ? 'page' : undefined}
+          >
+            {item.label}
+          </Link>
+        ))}
+      </nav>
+    </aside>
+  );
+}
diff --git a/apps/web/src/messages/de.json b/apps/web/src/messages/de.json
index 0519e1e..dcd040a 100644
--- a/apps/web/src/messages/de.json
+++ b/apps/web/src/messages/de.json
@@ -67,6 +67,7 @@
     "breadcrumb": {
       "home": "Startseite"
     },
+    "settings": "Einstellungen",
     "logout": "Abmelden",
     "role": {
       "SUPER_ADMIN": "Super-Admin",
@@ -98,6 +99,48 @@
     "empty": "Keine Widgets aktiv",
     "addWidget": "Widget hinzufuegen"
   },
+  "settings": {
+    "link": "Einstellungen",
+    "navLabel": "Einstellungen",
+    "backToDashboard": "Zurueck zum Dashboard",
+    "categoryDashboard": "Dashboard",
+    "categoryWidgets": "Widgets",
+    "categoryCalendar": "Kalender",
+    "sourceDeleteConfirm": "Moechten Sie diese Kalenderquelle wirklich loeschen?",
+    "sourceDeleteCta": "Quelle loeschen",
+    "providerDeleteConfirm": "Moechten Sie diesen Suchanbieter wirklich loeschen?",
+    "providerDeleteCta": "Anbieter loeschen",
+    "cancel": "Abbrechen"
+  },
+  "widgets": {
+    "emptyHeading": "Keine Widgets aktiv",
+    "emptyBody": "Klicken Sie auf Bearbeiten, um Widgets hinzuzufuegen.",
+    "addWidget": "Widget hinzufuegen",
+    "catalogTitle": "Widget hinzufuegen",
+    "deleteTooltip": "Widget entfernen",
+    "editMode": "Dashboard bearbeiten",
+    "saveChanges": "Aenderungen speichern",
+    "layoutLoadError": "Dashboard konnte nicht geladen werden. Bitte laden Sie die Seite neu.",
+    "widgetSaveError": "Aenderungen konnten nicht gespeichert werden. Bitte versuchen Sie es erneut.",
+    "clock.name": "Uhr",
+    "clock.description": "Zeigt die aktuelle Uhrzeit an",
+    "clock.dateHint": "Datum anzeigen",
+    "search.name": "Suchleiste",
+    "search.description": "Schnellsuche im Web",
+    "search.placeholder": "Suchen...",
+    "calendar.name": "Kalender",
+    "calendar.description": "Kommende Termine",
+    "calendar.emptyNoSources": "Keine Kalenderquellen konfiguriert",
+    "calendar.emptyNoEvents": "Keine anstehenden Termine",
+    "calendar.connectionSuccess": "Verbindung erfolgreich",
+    "calendar.connectionError": "Verbindung fehlgeschlagen. Bitte ueberpruefen Sie die URL und Zugangsdaten.",
+    "calendar.addSource": "Quelle hinzufuegen",
+    "calendar.sourceEmpty": "Keine Kalenderquellen eingerichtet. Fuegen Sie eine Quelle hinzu, um Termine anzuzeigen.",
+    "note.name": "Notizen",
+    "note.description": "Freitext-Notizen mit Markdown",
+    "note.defaultTitle": "Notiz",
+    "note.autosaveError": "Speichern fehlgeschlagen"
+  },
   "admin": {
     "users": {
       "title": "Benutzerverwaltung",
diff --git a/apps/web/src/messages/en.json b/apps/web/src/messages/en.json
index 5bf67ee..baecf91 100644
--- a/apps/web/src/messages/en.json
+++ b/apps/web/src/messages/en.json
@@ -67,6 +67,7 @@
     "breadcrumb": {
       "home": "Home"
     },
+    "settings": "Settings",
     "logout": "Sign Out",
     "role": {
       "SUPER_ADMIN": "Super Admin",
@@ -98,6 +99,48 @@
     "empty": "No active widgets",
     "addWidget": "Add widget"
   },
+  "settings": {
+    "link": "Settings",
+    "navLabel": "Settings",
+    "backToDashboard": "Back to Dashboard",
+    "categoryDashboard": "Dashboard",
+    "categoryWidgets": "Widgets",
+    "categoryCalendar": "Calendar",
+    "sourceDeleteConfirm": "Are you sure you want to delete this calendar source?",
+    "sourceDeleteCta": "Delete source",
+    "providerDeleteConfirm": "Are you sure you want to delete this search provider?",
+    "providerDeleteCta": "Delete provider",
+    "cancel": "Cancel"
+  },
+  "widgets": {
+    "emptyHeading": "No active widgets",
+    "emptyBody": "Click edit to add widgets to your dashboard.",
+    "addWidget": "Add widget",
+    "catalogTitle": "Add widget",
+    "deleteTooltip": "Remove widget",
+    "editMode": "Edit dashboard",
+    "saveChanges": "Save changes",
+    "layoutLoadError": "Could not load dashboard. Please reload the page.",
+    "widgetSaveError": "Could not save changes. Please try again.",
+    "clock.name": "Clock",
+    "clock.description": "Shows the current time",
+    "clock.dateHint": "Show date",
+    "search.name": "Search",
+    "search.description": "Quick web search",
+    "search.placeholder": "Search...",
+    "calendar.name": "Calendar",
+    "calendar.description": "Upcoming events",
+    "calendar.emptyNoSources": "No calendar sources configured",
+    "calendar.emptyNoEvents": "No upcoming events",
+    "calendar.connectionSuccess": "Connection successful",
+    "calendar.connectionError": "Connection failed. Please check the URL and credentials.",
+    "calendar.addSource": "Add source",
+    "calendar.sourceEmpty": "No calendar sources configured. Add a source to display events.",
+    "note.name": "Notes",
+    "note.description": "Free-text notes with Markdown",
+    "note.defaultTitle": "Note",
+    "note.autosaveError": "Save failed"
+  },
   "admin": {
     "users": {
       "title": "User Management",