diff --git a/app/config.py b/app/config.py
index 9df50a9..4e0b5ba 100644
--- a/app/config.py
+++ b/app/config.py
@@ -72,6 +72,8 @@ class Config(pydantic.BaseModel):
     code_highlighting_theme = "friendly_grayscale"
     blocked_servers: list[_BlockedServer] = []
 
+    inbox_retention_days: int = 15
+
     # Config items to make tests easier
     sqlalchemy_database: str | None = None
     key_path: str | None = None
@@ -118,6 +120,8 @@ if CONFIG.privacy_replace:
 
 BLOCKED_SERVERS = {blocked_server.hostname for blocked_server in CONFIG.blocked_servers}
 
+INBOX_RETENTION_DAYS = CONFIG.inbox_retention_days
+
 BASE_URL = ID
 DEBUG = CONFIG.debug
 DB_PATH = CONFIG.sqlalchemy_database or ROOT_DIR / "data" / "microblogpub.db"
diff --git a/app/prune.py b/app/prune.py
new file mode 100644
index 0000000..877b58f
--- /dev/null
+++ b/app/prune.py
@@ -0,0 +1,77 @@
+from datetime import timedelta
+
+from loguru import logger
+from sqlalchemy import and_
+from sqlalchemy import delete
+from sqlalchemy import not_
+
+from app import activitypub as ap
+from app import models
+from app.config import BASE_URL
+from app.config import INBOX_RETENTION_DAYS
+from app.database import AsyncSession
+from app.database import async_session
+from app.utils.datetime import now
+
+
+async def prune_old_data(
+    db_session: AsyncSession,
+) -> None:
+    logger.info(f"Pruning old data with {INBOX_RETENTION_DAYS=}")
+    await _prune_old_incoming_activities(db_session)
+    await _prune_old_inbox_objects(db_session)
+
+    await db_session.commit()
+    # Reclaim disk space
+    await db_session.execute("VACUUM")  # type: ignore
+
+
+async def _prune_old_incoming_activities(
+    db_session: AsyncSession,
+) -> None:
+    result = await db_session.execute(
+        delete(models.IncomingActivity)
+        .where(
+            models.IncomingActivity.created_at
+            < now() - timedelta(days=INBOX_RETENTION_DAYS),
+            # Keep failed activity for debug
+            models.IncomingActivity.is_errored.is_(False),
+        )
+        .execution_options(synchronize_session=False)
+    )
+    logger.info(f"Deleted {result.rowcount} old incoming activities")  # type: ignore
+
+
+async def _prune_old_inbox_objects(
+    db_session: AsyncSession,
+) -> None:
+    result = await db_session.execute(
+        delete(models.InboxObject)
+        .where(
+            # Keep bookmarked objects
+            models.InboxObject.is_bookmarked.is_(False),
+            # Keep liked objects
+            models.InboxObject.liked_via_outbox_object_ap_id.is_(None),
+            # Keep announced objects
+            models.InboxObject.announced_via_outbox_object_ap_id.is_(None),
+            # Keep objects related to local conversations
+            models.InboxObject.conversation.not_like(f"{BASE_URL}/%"),
+            # Keep direct messages
+            not_(
+                and_(
+                    models.InboxObject.visibility == ap.VisibilityEnum.DIRECT,
+                    models.InboxObject.ap_type.in_(["Note"]),
+                )
+            ),
+            # Filter by retention days
+            models.InboxObject.ap_published_at
+            < now() - timedelta(days=INBOX_RETENTION_DAYS),
+        )
+        .execution_options(synchronize_session=False)
+    )
+    logger.info(f"Deleted {result.rowcount} old inbox objects")  # type: ignore
+
+
+async def run_prune_old_data() -> None:
+    async with async_session() as db_session:
+        await prune_old_data(db_session)
diff --git a/tasks.py b/tasks.py
index e2e47b6..58f14f6 100644
--- a/tasks.py
+++ b/tasks.py
@@ -181,3 +181,11 @@ def build_docker_image(ctx):
     # type: (Context) -> None
     with embed_version():
         run("docker build -t microblogpub/microblogpub .")
+
+
+@task
+def prune_old_data(ctx):
+    # type: (Context) -> None
+    from app.prune import run_prune_old_data
+
+    asyncio.run(run_prune_old_data())