diff --git a/activities/models/fan_out.py b/activities/models/fan_out.py
index 40d73dd..de5fbf8 100644
--- a/activities/models/fan_out.py
+++ b/activities/models/fan_out.py
@@ -72,7 +72,10 @@ class FanOutStates(StateGraph):
                 try:
                     await post.author.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(post.to_create_ap()),
                     )
                 except httpx.RequestError:
@@ -85,7 +88,10 @@ class FanOutStates(StateGraph):
                 try:
                     await post.author.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(post.to_update_ap()),
                     )
                 except httpx.RequestError:
@@ -108,7 +114,10 @@ class FanOutStates(StateGraph):
                 try:
                     await post.author.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(post.to_delete_ap()),
                     )
                 except httpx.RequestError:
@@ -130,7 +139,10 @@ class FanOutStates(StateGraph):
                 try:
                     await interaction.identity.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(interaction.to_ap()),
                     )
                 except httpx.RequestError:
@@ -153,7 +165,10 @@ class FanOutStates(StateGraph):
                 try:
                     await interaction.identity.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(interaction.to_undo_ap()),
                     )
                 except httpx.RequestError:
@@ -165,7 +180,10 @@ class FanOutStates(StateGraph):
                 try:
                     await identity.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(fan_out.subject_identity.to_update_ap()),
                     )
                 except httpx.RequestError:
@@ -177,7 +195,10 @@ class FanOutStates(StateGraph):
                 try:
                     await identity.signed_request(
                         method="post",
-                        uri=fan_out.identity.inbox_uri,
+                        uri=(
+                            fan_out.identity.shared_inbox_uri
+                            or fan_out.identity.inbox_uri
+                        ),
                         body=canonicalise(fan_out.subject_identity.to_delete_ap()),
                     )
                 except httpx.RequestError:
@@ -214,6 +235,9 @@ class FanOut(StatorModel):
     state = StateField(FanOutStates)
 
     # The user this event is targeted at
+    # We always need this, but if there is a shared inbox URL on the user
+    # we'll deliver to that and won't have fanouts for anyone else with the
+    # same one.
     identity = models.ForeignKey(
         "users.Identity",
         on_delete=models.CASCADE,
diff --git a/activities/models/post.py b/activities/models/post.py
index ed28c83..74ea0b4 100644
--- a/activities/models/post.py
+++ b/activities/models/post.py
@@ -707,7 +707,20 @@ class Post(StatorModel):
         # If it's a local post, include the author
         if self.local:
             targets.add(self.author)
-        return targets
+        # Now dedupe the targets based on shared inboxes (we only keep one per
+        # shared inbox)
+        deduped_targets = set()
+        shared_inboxes = set()
+        for target in targets:
+            if target.local or not target.shared_inbox_uri:
+                deduped_targets.add(target)
+            elif target.shared_inbox_uri not in shared_inboxes:
+                shared_inboxes.add(target.shared_inbox_uri)
+                deduped_targets.add(target)
+            else:
+                # Their shared inbox is already being sent to
+                pass
+        return deduped_targets
 
     ### ActivityPub (inbound) ###
 
diff --git a/tests/activities/models/test_post_targets.py b/tests/activities/models/test_post_targets.py
index 0fbfdd6..5d235d5 100644
--- a/tests/activities/models/test_post_targets.py
+++ b/tests/activities/models/test_post_targets.py
@@ -2,7 +2,7 @@ import pytest
 from asgiref.sync import async_to_sync
 
 from activities.models import Post
-from users.models import Follow
+from users.models import Domain, Follow, Identity
 
 
 @pytest.mark.django_db
@@ -50,6 +50,59 @@ def test_post_targets_simple(identity, other_identity, remote_identity):
     assert targets == {other_identity}
 
 
+@pytest.mark.django_db
+def test_post_targets_shared(identity, other_identity):
+    """
+    Tests that remote identities with the same shared inbox only get one target.
+    """
+    # Create a pair of remote identities that share an inbox URI
+    domain = Domain.objects.create(domain="remote.test", local=False, state="updated")
+    remote1 = Identity.objects.create(
+        actor_uri="https://remote.test/test1/",
+        inbox_uri="https://remote.test/@test1/inbox/",
+        shared_inbox_uri="https://remote.test/inbox/",
+        profile_uri="https://remote.test/@test1/",
+        username="test1",
+        domain=domain,
+        name="Test1",
+        local=False,
+        state="updated",
+    )
+    remote2 = Identity.objects.create(
+        actor_uri="https://remote.test/test2/",
+        inbox_uri="https://remote.test/@test2/inbox/",
+        shared_inbox_uri="https://remote.test/inbox/",
+        profile_uri="https://remote.test/@test2/",
+        username="test2",
+        domain=domain,
+        name="Test2",
+        local=False,
+        state="updated",
+    )
+
+    # Make a post mentioning one local and two remote identities
+    post = Post.objects.create(
+        content="<p>Test</p>",
+        author=identity,
+        local=True,
+    )
+    post.mentions.add(other_identity)
+    post.mentions.add(remote1)
+    post.mentions.add(remote2)
+    targets = async_to_sync(post.aget_targets)()
+
+    # We should only have one of remote1 or remote2 in there as they share a
+    # shared inbox URI
+    assert (targets == {identity, other_identity, remote1}) or (
+        targets
+        == {
+            identity,
+            other_identity,
+            remote2,
+        }
+    )
+
+
 @pytest.mark.django_db
 def test_post_local_only(identity, other_identity, remote_identity):
     """