diff --git a/reservations/migrations/0002_externalreservation.py b/reservations/migrations/0002_externalreservation.py
new file mode 100644
index 0000000..9c0f2d2
--- /dev/null
+++ b/reservations/migrations/0002_externalreservation.py
@@ -0,0 +1,31 @@
+# Generated by Django 5.0.7 on 2024-08-06 17:17
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("reservations", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="ExternalReservation",
+            fields=[
+                (
+                    "reservation_ptr",
+                    models.OneToOneField(
+                        auto_created=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        parent_link=True,
+                        primary_key=True,
+                        serialize=False,
+                        to="reservations.reservation",
+                    ),
+                ),
+                ("title", models.CharField(max_length=1024)),
+            ],
+            bases=("reservations.reservation",),
+        ),
+    ]
diff --git a/reservations/models.py b/reservations/models.py
index 06cb9a2..40d58d7 100644
--- a/reservations/models.py
+++ b/reservations/models.py
@@ -132,3 +132,18 @@ class UserReservation(Reservation):
         return super().make_google_calendar_event() | {
             "summary": str(self.user),
         }
+
+
+class ExternalReservation(Reservation):
+    """Reservations created by something else in Google Calendar"""
+
+    title = models.CharField(max_length=1024)
+
+    def __str__(self) -> str:
+        return f'External "{self.title}" | {super().__str__()}'
+
+    def make_google_calendar_event(self):
+        """This should never be called, as these are reservations from Google Calendar and shouldn't be synced back"""
+        raise AttributeError(
+            "External Reservations should not be pushed back to Google Calendar"
+        )
diff --git a/reservations/tasks/sync_google_calendar.py b/reservations/tasks/sync_google_calendar.py
index 8622b3a..6af498d 100644
--- a/reservations/tasks/sync_google_calendar.py
+++ b/reservations/tasks/sync_google_calendar.py
@@ -10,7 +10,7 @@ from googleapiclient.discovery import build
 from googleapiclient.errors import HttpError
 
 from cmsmanage.django_q2_helper import q_task_group
-from reservations.models import Reservation, Resource
+from reservations.models import ExternalReservation, Reservation, Resource
 
 logger = logging.getLogger(__name__)
 
@@ -110,12 +110,21 @@ def sync_resource_from_google_calendar(
                     sendUpdates="none",
                 ).execute()
         else:
-            # TODO: handle external events (either Bookly or manually created)
-            # NOTE: this will also need to check for deleted events
             logger.debug(
-                "Event in Google Calendar not originated by CMSManage: skipping for now | %s",
+                "Event in Google Calendar not originated by CMSManage: adding/updating as external reservation | %s",
                 event["id"],
             )
+            # TODO: this might cause issues if something external
+            # creates events with matching IDs in different calendars
+            reservation, created = ExternalReservation.objects.update_or_create(
+                google_calendar_event_id=event["id"],
+                defaults={
+                    "title": event["summary"],
+                    "start": parse_google_calendar_datetime(event["start"]),
+                    "end": parse_google_calendar_datetime(event["end"]),
+                },
+            )
+            reservation.resources.add(resource)
 
     return {event["id"] for event in events}
 
@@ -135,32 +144,39 @@ def sync_resource_from_database(
 
         # reservation has an event id, so check if we already handled it earlier
         elif reservation.google_calendar_event_id not in existing_event_ids:
-            # this event was in Google Calendar at some point (possibly for a different
-            # resource/calendar), but did not appear in list(). Try to update it, then
-            # fall back to insert
-            logger.info(
-                "Reservation with event id not in Google Calendar: trying update | %s",
-                reservation.google_calendar_event_id,
-            )
-            try:
-                event = (
-                    service.events()
-                    .get(
-                        calendarId=resource.google_calendar,
-                        eventId=reservation.google_calendar_event_id,
-                    )
-                    .execute()
+            if isinstance(reservation, ExternalReservation):
+                logger.info(
+                    "External event in database did not exist in future of Google Calendar: deleting locally | %s",
+                    reservation.google_calendar_event_id,
                 )
-                update_calendar_event(service, resource, event, reservation)
-            except HttpError as error:
-                if error.status_code == HTTPStatus.NOT_FOUND:
-                    logger.info(
-                        "Event in database not in Google Calendar: inserting | %s",
-                        reservation.google_calendar_event_id,
+                reservation.delete()
+            else:
+                # this event was in Google Calendar at some point (possibly for a different
+                # resource/calendar), but did not appear in list(). Try to update it, then
+                # fall back to insert
+                logger.info(
+                    "Reservation with event id not in Google Calendar: trying update | %s",
+                    reservation.google_calendar_event_id,
+                )
+                try:
+                    event = (
+                        service.events()
+                        .get(
+                            calendarId=resource.google_calendar,
+                            eventId=reservation.google_calendar_event_id,
+                        )
+                        .execute()
                     )
-                    insert_calendar_event(service, resource, reservation)
-                else:
-                    raise
+                    update_calendar_event(service, resource, event, reservation)
+                except HttpError as error:
+                    if error.status_code == HTTPStatus.NOT_FOUND:
+                        logger.info(
+                            "Event in database not in Google Calendar: inserting | %s",
+                            reservation.google_calendar_event_id,
+                        )
+                        insert_calendar_event(service, resource, reservation)
+                    else:
+                        raise
 
 
 def sync_resource(service, resource: Resource, now: datetime):