diff --git a/app/agenda/page.tsx b/app/agenda/page.tsx
index b8e1450..3461ec8 100644
--- a/app/agenda/page.tsx
+++ b/app/agenda/page.tsx
@@ -44,10 +44,38 @@ export default async function CalendarPage() {
 
   const userId = session.user.username || session.user.email || '';
   
+  // Ensure user has a default private calendar (created automatically if missing)
+  // This is the user's personal calendar, distinct from Microsoft synced calendars
+  const defaultPrivateCalendarName = "Mon Calendrier";
+  const existingDefaultCalendar = await prisma.calendar.findFirst({
+    where: {
+      userId: session?.user?.id || '',
+      name: defaultPrivateCalendarName,
+      missionId: null, // Not a mission calendar
+      syncConfig: null, // Not a synced calendar
+    }
+  });
+
+  if (!existingDefaultCalendar) {
+    // Create default private calendar for the user
+    await prisma.calendar.create({
+      data: {
+        name: defaultPrivateCalendarName,
+        color: "#4f46e5", // Indigo color
+        description: "Votre calendrier personnel",
+        userId: session?.user?.id || '',
+        missionId: null,
+      }
+    });
+    console.log(`[AGENDA] Created default private calendar for user ${session?.user?.id}`);
+  }
+  
   // Get all calendars for the user with mission relation and sync configuration
   // This includes:
-  // 1. Personal calendars (userId = session.user.id)
-  // 2. Mission calendars where user is associated via MissionUser
+  // 1. Personal calendars (userId = session.user.id) - including the default private calendar
+  // 2. Microsoft synced calendars (named "Privée" with syncConfig)
+  // 3. Mission calendars where user is associated via MissionUser
+  // 4. Group calendars where user is a member
   // Exclude "Privée" and "Default" calendars that are not synced (they should only exist if synced from courrier)
   
   // Get personal calendars
diff --git a/app/api/calendars/route.ts b/app/api/calendars/route.ts
index cc6298e..f78e6c3 100644
--- a/app/api/calendars/route.ts
+++ b/app/api/calendars/route.ts
@@ -48,6 +48,32 @@ export async function GET(req: NextRequest) {
       userId: session.user.id,
     });
     
+    // Ensure user has a default private calendar (created automatically if missing)
+    const defaultPrivateCalendarName = "Mon Calendrier";
+    const existingDefaultCalendar = await prisma.calendar.findFirst({
+      where: {
+        userId: session.user.id,
+        name: defaultPrivateCalendarName,
+        missionId: null,
+        syncConfig: null,
+      }
+    });
+
+    if (!existingDefaultCalendar) {
+      await prisma.calendar.create({
+        data: {
+          name: defaultPrivateCalendarName,
+          color: "#4f46e5",
+          description: "Votre calendrier personnel",
+          userId: session.user.id,
+          missionId: null,
+        }
+      });
+      logger.debug('[CALENDAR] Created default private calendar', {
+        userId: session.user.id,
+      });
+    }
+    
     // Get user's personal calendars
     // Include syncConfig to filter "Privée"/"Default" calendars that don't have active sync
     const personalCalendars = await prisma.calendar.findMany({