diff --git a/lib/pleroma/group.ex b/lib/pleroma/group.ex
index 732791ec2..880cd52c6 100644
--- a/lib/pleroma/group.ex
+++ b/lib/pleroma/group.ex
@@ -92,4 +92,15 @@ defmodule Pleroma.Group do
       {:ok, group}
     end
   end
+
+  @spec get_for_object(map()) :: t() | nil
+  def get_for_object(%{"type" => "Group", "id" => id}) do
+    with %User{} = user <- User.get_cached_by_ap_id(id),
+         group <- Repo.preload(user, :group).group do
+      group
+    end
+  end
+
+  def get_for_object(%{"type" => "Create", "object" => object}), do: get_for_object(object)
+  def get_for_object(_), do: nil
 end
diff --git a/lib/pleroma/user.ex b/lib/pleroma/user.ex
index 1e5c87403..5d9016e96 100644
--- a/lib/pleroma/user.ex
+++ b/lib/pleroma/user.ex
@@ -18,6 +18,7 @@ defmodule Pleroma.User do
   alias Pleroma.Emoji
   alias Pleroma.FollowingRelationship
   alias Pleroma.Formatter
+  alias Pleroma.Group
   alias Pleroma.HTML
   alias Pleroma.Keys
   alias Pleroma.MFA
@@ -209,6 +210,9 @@ defmodule Pleroma.User do
       on_replace: :delete
     )
 
+    # Some `users` are actually groups. In this case, they can have a corresponding `Group`
+    has_one(:group, Group)
+
     timestamps()
   end
 
diff --git a/lib/pleroma/web/activity_pub/builder.ex b/lib/pleroma/web/activity_pub/builder.ex
index f56bfc600..08f017a51 100644
--- a/lib/pleroma/web/activity_pub/builder.ex
+++ b/lib/pleroma/web/activity_pub/builder.ex
@@ -12,6 +12,7 @@ defmodule Pleroma.Web.ActivityPub.Builder do
   alias Pleroma.Emoji
   alias Pleroma.Object
   alias Pleroma.User
+  alias Pleroma.Web
   alias Pleroma.Web.ActivityPub.Relay
   alias Pleroma.Web.ActivityPub.Utils
   alias Pleroma.Web.ActivityPub.Visibility
@@ -105,6 +106,30 @@ defmodule Pleroma.Web.ActivityPub.Builder do
      }, []}
   end
 
+  def group(owner, name \\ nil, description \\ nil) do
+    id = Ecto.UUID.generate()
+    ap_id = "#{Web.base_url()}/groups/#{id}"
+
+    {:ok,
+     %{
+       "id" => ap_id,
+       "type" => "Group",
+       "name" => name,
+       "summary" => description,
+       "following" => "#{ap_id}/following",
+       "followers" => "#{ap_id}/followers",
+       "members" => "#{ap_id}/members",
+       # attributedTo? owner? admin?
+       "attributedTo" => owner.ap_id
+     }, []}
+  end
+
+  def create_group(owner, params \\ %{}) do
+    with {:ok, group, _} <- group(owner, params[:name], params[:description]) do
+      create(owner, group, [])
+    end
+  end
+
   def create(actor, object, recipients) do
     context =
       if is_map(object) do
diff --git a/lib/pleroma/web/activity_pub/object_validator.ex b/lib/pleroma/web/activity_pub/object_validator.ex
index 297c19cc0..264ae5831 100644
--- a/lib/pleroma/web/activity_pub/object_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validator.ex
@@ -29,6 +29,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
   alias Pleroma.Web.ActivityPub.ObjectValidators.EmojiReactValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.EventValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.FollowValidator
+  alias Pleroma.Web.ActivityPub.ObjectValidators.GroupValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.LikeValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.QuestionValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.UndoValidator
@@ -37,6 +38,16 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
   @impl true
   def validate(object, meta)
 
+  def validate(%{"type" => "Group"} = object, meta) do
+    with {:ok, object} <-
+           object
+           |> GroupValidator.cast_and_validate()
+           |> Ecto.Changeset.apply_action(:insert) do
+      object = stringify_keys(object)
+      {:ok, object, meta}
+    end
+  end
+
   def validate(%{"type" => type} = object, meta)
       when type in ~w[Accept Reject] do
     with {:ok, object} <-
diff --git a/lib/pleroma/web/activity_pub/object_validators/group_validator.ex b/lib/pleroma/web/activity_pub/object_validators/group_validator.ex
new file mode 100644
index 000000000..cf7ae36c5
--- /dev/null
+++ b/lib/pleroma/web/activity_pub/object_validators/group_validator.ex
@@ -0,0 +1,40 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.ObjectValidators.GroupValidator do
+  use Ecto.Schema
+
+  alias Pleroma.EctoType.ActivityPub.ObjectValidators
+
+  import Ecto.Changeset
+
+  @primary_key false
+
+  embedded_schema do
+    field(:id, ObjectValidators.ObjectID, primary_key: true)
+    field(:type, :string)
+  end
+
+  def cast_and_validate(data) do
+    data
+    |> cast_data()
+    |> validate_data()
+  end
+
+  def cast_data(data) do
+    %__MODULE__{}
+    |> changeset(data)
+  end
+
+  def changeset(struct, data) do
+    struct
+    |> cast(data, __schema__(:fields))
+  end
+
+  def validate_data(data_cng) do
+    data_cng
+    |> validate_inclusion(:type, ["Group"])
+    |> validate_required([:id])
+  end
+end
diff --git a/lib/pleroma/web/common_api.ex b/lib/pleroma/web/common_api.ex
index b003e30c7..400fe00c9 100644
--- a/lib/pleroma/web/common_api.ex
+++ b/lib/pleroma/web/common_api.ex
@@ -30,6 +30,13 @@ defmodule Pleroma.Web.CommonAPI do
     end
   end
 
+  def create_group(user, params) do
+    with {:ok, group_data, _} <- Builder.create_group(user, params),
+         {:ok, group, _} <- Pipeline.common_pipeline(group_data, local: true) do
+      {:ok, group}
+    end
+  end
+
   def post_chat_message(%User{} = user, %User{} = recipient, content, opts \\ []) do
     with maybe_attachment <- opts[:media_id] && Object.get_by_id(opts[:media_id]),
          :ok <- validate_chat_content_length(content, !!maybe_attachment),
diff --git a/priv/repo/migrations/20210113150220_create_groups.exs b/priv/repo/migrations/20210113150220_create_groups.exs
index 642326d51..e98be498e 100644
--- a/priv/repo/migrations/20210113150220_create_groups.exs
+++ b/priv/repo/migrations/20210113150220_create_groups.exs
@@ -6,7 +6,6 @@ defmodule Pleroma.Repo.Migrations.CreateGroups do
       add(:id, :uuid, primary_key: true)
       add(:user_id, references(:users, type: :uuid, on_delete: :delete_all), null: false)
       add(:owner_id, references(:users, type: :uuid, on_delete: :nilify_all))
-      add(:members, {:array, :string}, default: [])
       add(:name, :text)
       add(:description, :text)
       add(:members_collection, :text)
diff --git a/test/pleroma/group_test.exs b/test/pleroma/group_test.exs
index e4c6cfd92..c10dd10f4 100644
--- a/test/pleroma/group_test.exs
+++ b/test/pleroma/group_test.exs
@@ -10,6 +10,32 @@ defmodule Pleroma.GroupTest do
 
   import Pleroma.Factory
 
+  test "get_for_object/1 gets a group based on the group object or the create activity" do
+    user = insert(:user)
+
+    {:ok, group} = Group.create(%{owner_id: user.id, name: "cofe", description: "corndog"})
+    group = Repo.preload(group, :user)
+
+    group_object = %{
+      "id" => group.user.ap_id,
+      "type" => "Group"
+    }
+
+    assert group.id == Group.get_for_object(group_object).id
+
+    # Same works if wrapped in a 'create'
+    group_create = %{
+      "type" => "Create",
+      "object" => group_object
+    }
+
+    assert group.id == Group.get_for_object(group_create).id
+
+    # Nil for nonsense
+
+    assert nil == Group.get_for_object(%{"nothing" => "PS4 games"})
+  end
+
   test "a user can create a group" do
     user = insert(:user)
     {:ok, group} = Group.create(%{owner_id: user.id, name: "cofe", description: "corndog"})
diff --git a/test/pleroma/web/activity_pub/object_validators/group_validation_test.exs b/test/pleroma/web/activity_pub/object_validators/group_validation_test.exs
new file mode 100644
index 000000000..3aab7493d
--- /dev/null
+++ b/test/pleroma/web/activity_pub/object_validators/group_validation_test.exs
@@ -0,0 +1,24 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.ObjectValidators.GroupValidationTest do
+  use Pleroma.DataCase, async: true
+
+  import Pleroma.Factory
+
+  alias Pleroma.Web.ActivityPub.Builder
+  alias Pleroma.Web.ActivityPub.ObjectValidator
+
+  describe "Group objects" do
+    test "it validates a group" do
+      user = insert(:user)
+
+      {:ok, group_data, []} = Builder.group(user, "a group", "a description")
+
+      {:ok, group, _} = ObjectValidator.validate(group_data, [])
+
+      assert group
+    end
+  end
+end
diff --git a/test/pleroma/web/common_api/group_messaging_test.exs b/test/pleroma/web/common_api/group_messaging_test.exs
new file mode 100644
index 000000000..2509428ae
--- /dev/null
+++ b/test/pleroma/web/common_api/group_messaging_test.exs
@@ -0,0 +1,25 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.CommonAPI.GroupMessagingTest do
+  use Pleroma.DataCase
+
+  import Pleroma.Factory
+
+  alias Pleroma.Group
+  alias Pleroma.Web.CommonAPI
+
+  describe "Group chats" do
+    test "local chat" do
+      user = insert(:user)
+
+      {:ok, group_creation_activity} =
+        CommonAPI.create_group(user, %{name: "cofe", description: "for cofe enthusiasts"})
+
+      group = Group.get_for_object(group_creation_activity)
+
+      assert group
+    end
+  end
+end