diff --git a/lib/mv_web/live/member_live/index.ex b/lib/mv_web/live/member_live/index.ex
index 881be53..41f08c9 100644
--- a/lib/mv_web/live/member_live/index.ex
+++ b/lib/mv_web/live/member_live/index.ex
@@ -85,6 +85,12 @@ defmodule MvWeb.MemberLive.Index do
       |> Enum.filter(&(&1.value_type == :boolean))
       |> Enum.sort_by(& &1.name, :asc)
 
+    # Load groups for filter dropdown (sorted by name)
+    groups =
+      Mv.Membership.Group
+      |> Ash.Query.sort(name: :asc)
+      |> Ash.read!(actor: actor)
+
     # Load settings once to avoid N+1 queries
     settings =
       case Membership.get_settings() do
@@ -115,6 +121,8 @@ defmodule MvWeb.MemberLive.Index do
       |> assign_new(:sort_field, fn -> :first_name end)
       |> assign_new(:sort_order, fn -> :asc end)
       |> assign(:cycle_status_filter, nil)
+      |> assign(:group_filter, nil)
+      |> assign(:groups, groups)
       |> assign(:boolean_custom_field_filters, %{})
       |> assign(:selected_members, MapSet.new())
       |> assign(:settings, settings)
@@ -242,6 +250,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.sort_field,
         socket.assigns.sort_order,
         socket.assigns.cycle_status_filter,
+        socket.assigns[:group_filter],
         new_show_current,
         socket.assigns.boolean_custom_field_filters
       )
@@ -255,6 +264,35 @@ defmodule MvWeb.MemberLive.Index do
     {:noreply, push_patch(socket, to: new_path, replace: true)}
   end
 
+  @impl true
+  def handle_event("group_filter_changed", %{"group_filter" => group_id_param}, socket) do
+    group_filter = normalize_group_filter(group_id_param, socket.assigns.groups)
+
+    socket =
+      socket
+      |> assign(:group_filter, group_filter)
+      |> load_members()
+      |> update_selection_assigns()
+
+    query_params =
+      build_query_params(
+        socket.assigns.query,
+        socket.assigns.sort_field,
+        socket.assigns.sort_order,
+        socket.assigns.cycle_status_filter,
+        group_filter,
+        socket.assigns.show_current_cycle,
+        socket.assigns.boolean_custom_field_filters
+      )
+      |> maybe_add_field_selection(
+        socket.assigns[:user_field_selection],
+        socket.assigns[:fields_in_url?] || false
+      )
+
+    new_path = ~p"/members?#{query_params}"
+    {:noreply, push_patch(socket, to: new_path, replace: true)}
+  end
+
   @impl true
   def handle_event("copy_emails", _params, socket) do
     selected_ids = socket.assigns.selected_members
@@ -352,6 +390,7 @@ defmodule MvWeb.MemberLive.Index do
         export_sort_field(socket.assigns.sort_field),
         export_sort_order(socket.assigns.sort_order),
         socket.assigns.cycle_status_filter,
+        socket.assigns[:group_filter],
         socket.assigns.show_current_cycle,
         socket.assigns.boolean_custom_field_filters
       )
@@ -377,6 +416,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.sort_field,
         socket.assigns.sort_order,
         socket.assigns.cycle_status_filter,
+        socket.assigns[:group_filter],
         socket.assigns.show_current_cycle,
         socket.assigns.boolean_custom_field_filters
       )
@@ -404,6 +444,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.sort_field,
         socket.assigns.sort_order,
         filter,
+        socket.assigns[:group_filter],
         socket.assigns.show_current_cycle,
         socket.assigns.boolean_custom_field_filters
       )
@@ -437,6 +478,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.sort_field,
         socket.assigns.sort_order,
         socket.assigns.cycle_status_filter,
+        socket.assigns[:group_filter],
         socket.assigns.show_current_cycle,
         updated_filters
       )
@@ -454,6 +496,7 @@ defmodule MvWeb.MemberLive.Index do
     socket =
       socket
       |> assign(:cycle_status_filter, cycle_status_filter)
+      |> assign(:group_filter, nil)
       |> assign(:boolean_custom_field_filters, boolean_filters)
       |> load_members()
       |> update_selection_assigns()
@@ -464,6 +507,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.sort_field,
         socket.assigns.sort_order,
         cycle_status_filter,
+        socket.assigns[:group_filter],
         socket.assigns.show_current_cycle,
         boolean_filters
       )
@@ -600,6 +644,7 @@ defmodule MvWeb.MemberLive.Index do
       |> maybe_update_search(params)
       |> maybe_update_sort(params)
       |> maybe_update_cycle_status_filter(params)
+      |> maybe_update_group_filter(params)
       |> maybe_update_boolean_filters(params)
       |> maybe_update_show_current_cycle(params)
       |> assign(:fields_in_url?, fields_in_url?)
@@ -633,6 +678,7 @@ defmodule MvWeb.MemberLive.Index do
       socket.assigns.sort_field,
       socket.assigns.sort_order,
       socket.assigns.cycle_status_filter,
+      socket.assigns[:group_filter],
       socket.assigns.show_current_cycle,
       socket.assigns.boolean_custom_field_filters,
       socket.assigns.user_field_selection,
@@ -726,6 +772,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.sort_field,
         socket.assigns.sort_order,
         socket.assigns.cycle_status_filter,
+        socket.assigns[:group_filter],
         socket.assigns.show_current_cycle,
         socket.assigns.boolean_custom_field_filters
       )
@@ -744,6 +791,7 @@ defmodule MvWeb.MemberLive.Index do
          sort_field,
          sort_order,
          cycle_status_filter,
+         group_filter,
          show_current_cycle,
          boolean_filters
        ) do
@@ -774,6 +822,13 @@ defmodule MvWeb.MemberLive.Index do
         :unpaid -> Map.put(base_params, "cycle_status_filter", "unpaid")
       end
 
+    base_params =
+      if group_filter && group_filter != "" do
+        Map.put(base_params, "group_filter", to_string(group_filter))
+      else
+        base_params
+      end
+
     base_params =
       if show_current_cycle do
         Map.put(base_params, "show_current_cycle", "true")
@@ -823,8 +878,14 @@ defmodule MvWeb.MemberLive.Index do
 
     query = MembershipFeeStatus.load_cycles_for_members(query, socket.assigns.show_current_cycle)
 
+    # Load groups for each member (id, name, slug only)
+    query =
+      Ash.Query.load(query, groups: [:id, :name, :slug])
+
     query = apply_search_filter(query, search_query)
 
+    query = apply_group_filter(query, socket.assigns[:group_filter])
+
     # Use ALL custom fields for sorting (not just show_in_overview subset)
     custom_fields_for_sort = socket.assigns.all_custom_fields
 
@@ -860,7 +921,7 @@ defmodule MvWeb.MemberLive.Index do
         socket.assigns.all_custom_fields
       )
 
-    # Sort in memory if needed (custom fields only; computed fields are blocked)
+    # Sort in memory if needed (custom fields, groups, group_count; computed fields are blocked)
     members =
       if sort_after_load and
            socket.assigns.sort_field not in FieldVisibility.computed_member_fields() do
@@ -902,6 +963,13 @@ defmodule MvWeb.MemberLive.Index do
     end
   end
 
+  defp apply_group_filter(query, nil), do: query
+  defp apply_group_filter(query, ""), do: query
+
+  defp apply_group_filter(query, group_id) when is_binary(group_id) do
+    Ash.Query.filter(query, expr(exists(groups, id == ^group_id)))
+  end
+
   defp apply_cycle_status_filter(members, nil, _show_current), do: members
 
   defp apply_cycle_status_filter(members, status, show_current)
@@ -937,6 +1005,10 @@ defmodule MvWeb.MemberLive.Index do
 
   defp apply_sort_to_query(query, field, order) do
     cond do
+      # Groups sort -> after load (in memory)
+      field in [:groups, "groups"] ->
+        {query, true}
+
       # Custom field sort -> after load
       custom_field_sort?(field) ->
         {query, true}
@@ -976,11 +1048,12 @@ defmodule MvWeb.MemberLive.Index do
   defp valid_sort_field_db_or_custom?(field) when is_atom(field) do
     non_sortable_fields = [:notes]
     valid_fields = Mv.Constants.member_fields() -- non_sortable_fields
-    field in valid_fields or custom_field_sort?(field)
+    field in valid_fields or custom_field_sort?(field) or field == :groups
   end
 
   defp valid_sort_field_db_or_custom?(field) when is_binary(field) do
-    custom_field_sort?(field) or
+    field == "groups" or
+      custom_field_sort?(field) or
       ((atom = safe_member_field_atom_only(field)) != nil and valid_sort_field_db_or_custom?(atom))
   end
 
@@ -1024,14 +1097,37 @@ defmodule MvWeb.MemberLive.Index do
   end
 
   defp sort_members_in_memory(members, field, order, custom_fields) do
-    custom_field_id_str = extract_custom_field_id(field)
+    cond do
+      field in [:groups, "groups"] ->
+        sort_members_by_groups(members, order)
 
-    case custom_field_id_str do
-      nil -> members
-      id_str -> sort_members_by_custom_field(members, id_str, order, custom_fields)
+      true ->
+        custom_field_id_str = extract_custom_field_id(field)
+
+        case custom_field_id_str do
+          nil -> members
+          id_str -> sort_members_by_custom_field(members, id_str, order, custom_fields)
+        end
     end
   end
 
+  defp sort_members_by_groups(members, order) do
+    # Members with groups first, then by first group name alphabetically
+    first_group_name = fn member ->
+      groups = member.groups || []
+      names = Enum.map(groups, & &1.name) |> Enum.sort()
+      List.first(names)
+    end
+
+    members
+    |> Enum.sort_by(fn member ->
+      name = first_group_name.(member)
+      # Nil (no groups) sorts last in asc, first in desc
+      {name == nil, name || ""}
+    end)
+    |> then(fn list -> if order == :desc, do: Enum.reverse(list), else: list end)
+  end
+
   defp sort_members_by_custom_field(members, id_str, order, custom_fields) do
     custom_field = find_custom_field_by_id(custom_fields, id_str)
 
@@ -1126,11 +1222,12 @@ defmodule MvWeb.MemberLive.Index do
   defp determine_field(default, _), do: default
 
   defp determine_field_after_computed_check(default, sf) when is_binary(sf) do
-    if custom_field_sort?(sf) do
-      if valid_sort_field?(sf), do: sf, else: default
-    else
-      atom = safe_member_field_atom_only(sf)
-      if atom != nil and valid_sort_field?(atom), do: atom, else: default
+    cond do
+      sf == "groups" -> :groups
+      custom_field_sort?(sf) -> if valid_sort_field?(sf), do: sf, else: default
+      true ->
+        atom = safe_member_field_atom_only(sf)
+        if atom != nil and valid_sort_field?(atom), do: atom, else: default
     end
   end
 
@@ -1160,6 +1257,32 @@ defmodule MvWeb.MemberLive.Index do
   defp maybe_update_cycle_status_filter(socket, _params),
     do: assign(socket, :cycle_status_filter, nil)
 
+  defp maybe_update_group_filter(socket, %{"group_filter" => group_id_param}) do
+    group_filter = normalize_group_filter(group_id_param, socket.assigns.groups)
+    assign(socket, :group_filter, group_filter)
+  end
+
+  defp maybe_update_group_filter(socket, _params), do: socket
+
+  defp normalize_group_filter("", _groups), do: nil
+  defp normalize_group_filter(nil, _groups), do: nil
+
+  defp normalize_group_filter(group_id_param, groups) when is_binary(group_id_param) do
+    case Ecto.UUID.cast(group_id_param) do
+      {:ok, _uuid} ->
+        if Enum.any?(groups, fn g -> to_string(g.id) == group_id_param end) do
+          group_id_param
+        else
+          nil
+        end
+
+      :error ->
+        nil
+    end
+  end
+
+  defp normalize_group_filter(_, _), do: nil
+
   defp determine_cycle_status_filter("paid"), do: :paid
   defp determine_cycle_status_filter("unpaid"), do: :unpaid
   defp determine_cycle_status_filter(_), do: nil
diff --git a/lib/mv_web/live/member_live/index.html.heex b/lib/mv_web/live/member_live/index.html.heex
index 381cd63..b72e598 100644
--- a/lib/mv_web/live/member_live/index.html.heex
+++ b/lib/mv_web/live/member_live/index.html.heex
@@ -52,6 +52,22 @@
       query={@query}
       placeholder={gettext("Search...")}
     />
+    <form id="group-filter-form" phx-change="group_filter_changed" class="contents">
+      <select
+        name="group_filter"
+        class="select select-bordered select-sm max-w-xs"
+        aria-label={gettext("Filter by group")}
+      >
+        <option value="" selected={@group_filter == nil}>
+          {gettext("All groups")}
+        </option>
+        <%= for group <- @groups do %>
+          <option value={group.id} selected={@group_filter == to_string(group.id)}>
+            {group.name}
+          </option>
+        <% end %>
+      </select>
+    </form>
     <.live_component
       module={MvWeb.Components.MemberFilterComponent}
       id="member-filter"
@@ -310,6 +326,34 @@
         <span class="badge badge-ghost">{gettext("No cycle")}</span>
       <% end %>
     </:col>
+    <:col
+      :let={member}
+      label={
+        ~H"""
+        <.live_component
+          module={MvWeb.Components.SortHeaderComponent}
+          id={:sort_groups}
+          field={:groups}
+          label={gettext("Groups")}
+          sort_field={@sort_field}
+          sort_order={@sort_order}
+        />
+        """
+      }
+    >
+      <%= for group <- (member.groups || []) do %>
+        <span
+          class="badge badge-outline badge-primary"
+          role="status"
+          aria-label={gettext("Member of group %{name}", name: group.name)}
+        >
+          {group.name}
+        </span>
+      <% end %>
+      <%= if (member.groups || []) == [] do %>
+        <span class="text-base-content/50">—</span>
+      <% end %>
+    </:col>
     <:action :let={member}>
       <div class="sr-only">
         <.link navigate={~p"/members/#{member}"}>{gettext("Show")}</.link>
diff --git a/mix.lock b/mix.lock
index f698fa5..98e8726 100644
--- a/mix.lock
+++ b/mix.lock
@@ -72,7 +72,7 @@
   "sobelow": {:hex, :sobelow, "0.14.1", "2f81e8632f15574cba2402bcddff5497b413c01e6f094bc0ab94e83c2f74db81", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "8fac9a2bd90fdc4b15d6fca6e1608efb7f7c600fa75800813b794ee9364c87f2"},
   "sourceror": {:hex, :sourceror, "1.10.1", "325753ed460fe9fa34ebb4deda76d57b2e1507dcd78a5eb9e1c41bfb78b7cdfe", [:mix], [], "hexpm", "288f3079d93865cd1e3e20df5b884ef2cb440e0e03e8ae393624ee8a770ba588"},
   "spark": {:hex, :spark, "2.4.0", "f93d3ae6b5f3004e956d52f359fa40670366685447631bc7c058f4fbf250ebf3", [:mix], [{:igniter, ">= 0.3.64 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: true]}, {:sourceror, "~> 1.2", [hex: :sourceror, repo: "hexpm", optional: true]}], "hexpm", "4e5185f5737cd987bb9ef377ae3462a55b8312f5007c2bc4ad6e850d14ac0111"},
-  "spitfire": {:hex, :spitfire, "0.3.3", "be195b27648f21454932bf46014455cdbce4fca55fef1f0e41d36076c47b6c4a", [], [], "hexpm", "5dc51c3b61a1d98cdcac1c130f0a374d22d51beed982df90834bdd616356e1fa"},
+  "spitfire": {:hex, :spitfire, "0.3.3", "be195b27648f21454932bf46014455cdbce4fca55fef1f0e41d36076c47b6c4a", [:mix], [], "hexpm", "5dc51c3b61a1d98cdcac1c130f0a374d22d51beed982df90834bdd616356e1fa"},
   "splode": {:hex, :splode, "0.3.0", "ff8effecc509a51245df2f864ec78d849248647c37a75886033e3b1a53ca9470", [:mix], [], "hexpm", "73cfd0892d7316d6f2c93e6e8784bd6e137b2aa38443de52fd0a25171d106d81"},
   "stream_data": {:hex, :stream_data, "1.2.0", "58dd3f9e88afe27dc38bef26fce0c84a9e7a96772b2925c7b32cd2435697a52b", [:mix], [], "hexpm", "eb5c546ee3466920314643edf68943a5b14b32d1da9fe01698dc92b73f89a9ed"},
   "sweet_xml": {:hex, :sweet_xml, "0.7.5", "803a563113981aaac202a1dbd39771562d0ad31004ddbfc9b5090bdcd5605277", [:mix], [], "hexpm", "193b28a9b12891cae351d81a0cead165ffe67df1b73fe5866d10629f4faefb12"},
diff --git a/test/mv_web/member_live/index_groups_display_test.exs b/test/mv_web/member_live/index_groups_display_test.exs
new file mode 100644
index 0000000..120d3ae
--- /dev/null
+++ b/test/mv_web/member_live/index_groups_display_test.exs
@@ -0,0 +1,97 @@
+defmodule MvWeb.MemberLive.IndexGroupsDisplayTest do
+  @moduledoc """
+  Tests for displaying groups in the member overview.
+
+  Tests cover:
+  - Group badges are displayed for members in groups
+  - Multiple badges for members in multiple groups
+  - No badge for members without groups
+  - Badge shows group name correctly
+  """
+  use MvWeb.ConnCase, async: false
+  import Phoenix.LiveViewTest
+  require Ash.Query
+
+  alias Mv.Membership.{Group, MemberGroup}
+
+  setup do
+    system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+    {:ok, member1} =
+      Mv.Membership.create_member(
+        %{first_name: "Alice", last_name: "Anderson", email: "alice@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, member2} =
+      Mv.Membership.create_member(
+        %{first_name: "Bob", last_name: "Brown", email: "bob@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, member3} =
+      Mv.Membership.create_member(
+        %{first_name: "Charlie", last_name: "Clark", email: "charlie@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, group1} =
+      Group
+      |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, group2} =
+      Group
+      |> Ash.Changeset.for_create(:create, %{name: "Active Members"})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg1} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member1.id, group_id: group1.id})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg2} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member1.id, group_id: group2.id})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg3} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member2.id, group_id: group1.id})
+      |> Ash.create(actor: system_actor)
+
+    %{member1: member1, member2: member2, member3: member3, group1: group1, group2: group2}
+  end
+
+  test "displays group badges for members in groups", %{conn: conn, group1: group1, group2: group2} do
+    conn = conn_with_oidc_user(conn)
+    {:ok, _view, html} = live(conn, "/members")
+    assert html =~ group1.name
+    assert html =~ group2.name
+  end
+
+  test "displays multiple badges for member in multiple groups", %{
+    conn: conn,
+    member1: member1,
+    group1: group1,
+    group2: group2
+  } do
+    conn = conn_with_oidc_user(conn)
+    {:ok, _view, html} = live(conn, "/members")
+    assert html =~ member1.first_name
+    assert html =~ group1.name
+    assert html =~ group2.name
+  end
+
+  test "shows placeholder for members without groups", %{conn: conn, member3: member3} do
+    conn = conn_with_oidc_user(conn)
+    {:ok, _view, html} = live(conn, "/members")
+    assert html =~ member3.first_name
+  end
+
+  test "displays group name correctly in badge", %{conn: conn, group1: group1} do
+    conn = conn_with_oidc_user(conn)
+    {:ok, _view, html} = live(conn, "/members")
+    assert html =~ group1.name
+  end
+end
diff --git a/test/mv_web/member_live/index_groups_filter_test.exs b/test/mv_web/member_live/index_groups_filter_test.exs
new file mode 100644
index 0000000..fb5cce9
--- /dev/null
+++ b/test/mv_web/member_live/index_groups_filter_test.exs
@@ -0,0 +1,113 @@
+defmodule MvWeb.MemberLive.IndexGroupsFilterTest do
+  @moduledoc """
+  Tests for filtering members by group in the member overview.
+  """
+  use MvWeb.ConnCase, async: false
+  import Phoenix.LiveViewTest
+  require Ash.Query
+
+  alias Mv.Membership.{Group, MemberGroup}
+
+  setup do
+    system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+    {:ok, member1} =
+      Mv.Membership.create_member(
+        %{first_name: "Alice", last_name: "Anderson", email: "alice@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, member2} =
+      Mv.Membership.create_member(
+        %{first_name: "Bob", last_name: "Brown", email: "bob@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, member3} =
+      Mv.Membership.create_member(
+        %{first_name: "Charlie", last_name: "Clark", email: "charlie@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, group1} =
+      Group
+      |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, group2} =
+      Group
+      |> Ash.Changeset.for_create(:create, %{name: "Active Members"})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg1} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member1.id, group_id: group1.id})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg2} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member2.id, group_id: group2.id})
+      |> Ash.create(actor: system_actor)
+
+    %{member1: member1, member2: member2, member3: member3, group1: group1, group2: group2}
+  end
+
+  test "filter 'All groups' shows all members", %{conn: conn, member1: m1, member2: m2, member3: m3} do
+    conn = conn_with_oidc_user(conn)
+    {:ok, _view, html} = live(conn, "/members")
+    assert html =~ m1.first_name
+    assert html =~ m2.first_name
+    assert html =~ m3.first_name
+  end
+
+  test "filter by specific group shows only members in that group", %{
+    conn: conn,
+    member1: m1,
+    member2: m2,
+    member3: m3,
+    group1: group1
+  } do
+    conn = conn_with_oidc_user(conn)
+    {:ok, view, _html} = live(conn, "/members")
+
+    view
+    |> element("#group-filter-form")
+    |> render_change(%{"group_filter" => group1.id})
+
+    html = render(view)
+    assert html =~ m1.first_name
+    refute html =~ m2.first_name
+    refute html =~ m3.first_name
+  end
+
+  test "filter persists in URL parameters", %{conn: conn, group1: group1, member1: m1} do
+    conn = conn_with_oidc_user(conn)
+    {:ok, view, _html} = live(conn, "/members")
+
+    view
+    |> element("#group-filter-form")
+    |> render_change(%{"group_filter" => group1.id})
+
+    # Verify filter is applied
+    html = render(view)
+    assert html =~ m1.first_name
+
+    # Verify visiting with group_filter in URL shows same filtered list
+    {:ok, _view2, html2} = live(conn, "/members?group_filter=#{group1.id}")
+    assert html2 =~ m1.first_name
+  end
+
+  test "filter is restored from URL on load", %{
+    conn: conn,
+    member1: m1,
+    member2: m2,
+    member3: m3,
+    group1: group1
+  } do
+    conn = conn_with_oidc_user(conn)
+    {:ok, _view, html} = live(conn, "/members?group_filter=#{group1.id}")
+    assert html =~ m1.first_name
+    refute html =~ m2.first_name
+    refute html =~ m3.first_name
+  end
+end
diff --git a/test/mv_web/member_live/index_groups_sorting_test.exs b/test/mv_web/member_live/index_groups_sorting_test.exs
new file mode 100644
index 0000000..204caf3
--- /dev/null
+++ b/test/mv_web/member_live/index_groups_sorting_test.exs
@@ -0,0 +1,69 @@
+defmodule MvWeb.MemberLive.IndexGroupsSortingTest do
+  @moduledoc """
+  Tests for sorting by groups in the member overview.
+  """
+  use MvWeb.ConnCase, async: false
+  import Phoenix.LiveViewTest
+  require Ash.Query
+
+  alias Mv.Membership.{Group, MemberGroup}
+
+  setup do
+    system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+    {:ok, member1} =
+      Mv.Membership.create_member(
+        %{first_name: "Alice", last_name: "Anderson", email: "alice@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, member2} =
+      Mv.Membership.create_member(
+        %{first_name: "Bob", last_name: "Brown", email: "bob@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, member4} =
+      Mv.Membership.create_member(
+        %{first_name: "David", last_name: "Davis", email: "david@example.com"},
+        actor: system_actor
+      )
+
+    {:ok, group_a} =
+      Group
+      |> Ash.Changeset.for_create(:create, %{name: "A Group"})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, group_b} =
+      Group
+      |> Ash.Changeset.for_create(:create, %{name: "B Group"})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg1} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member1.id, group_id: group_a.id})
+      |> Ash.create(actor: system_actor)
+
+    {:ok, _mg2} =
+      MemberGroup
+      |> Ash.Changeset.for_create(:create, %{member_id: member2.id, group_id: group_b.id})
+      |> Ash.create(actor: system_actor)
+
+    %{member1: member1, member2: member2, member4: member4, group_a: group_a, group_b: group_b}
+  end
+
+  test "sorts by group name ascending", %{conn: conn, group_a: group_a} do
+    conn = conn_with_oidc_user(conn)
+    {:ok, view, _html} = live(conn, "/members")
+
+    view
+    |> element("[data-testid='groups']")
+    |> render_click()
+
+    # Sort was applied: button shows ascending state and group names still visible
+    assert has_element?(view, "[data-testid='groups']")
+    html = render(view)
+    assert html =~ group_a.name
+  end
+
+end