diff --git a/lib/microwaveprop/radio.ex b/lib/microwaveprop/radio.ex
index 01197a51..1b50de27 100644
--- a/lib/microwaveprop/radio.ex
+++ b/lib/microwaveprop/radio.ex
@@ -449,7 +449,9 @@ defmodule Microwaveprop.Radio do
 
   @spec get_contact!(Ecto.UUID.t()) :: Contact.t()
   def get_contact!(id) do
-    Repo.get!(Contact, id)
+    Contact
+    |> Repo.get!(id)
+    |> Repo.preload(:flagged_by_user)
   end
 
   @doc """
@@ -463,10 +465,40 @@ defmodule Microwaveprop.Radio do
   def can_view?(%Contact{user_id: user_id}, %Scope{user: %User{id: user_id}}) when not is_nil(user_id), do: true
   def can_view?(%Contact{}, _scope), do: false
 
-  @spec toggle_flagged_invalid!(Contact.t()) :: Contact.t()
-  def toggle_flagged_invalid!(contact) do
+  @doc """
+  Hard-delete a contact and everything attached to it. All FK
+  references (`terrain_profiles`, `contact_edits`,
+  `contact_common_volume_radar`) declare `on_delete: :delete_all`,
+  so a single `Repo.delete!` cascades through.
+
+  Admin-only operation — callers must gate with `is_admin` before
+  invoking. Irreversible: prefer `toggle_flagged_invalid!/2` when
+  the data should be hidden but kept in the audit trail.
+  """
+  @spec delete_contact!(Contact.t()) :: Contact.t()
+  def delete_contact!(%Contact{} = contact), do: Repo.delete!(contact)
+
+  @spec toggle_flagged_invalid!(Contact.t(), User.t() | nil) :: Contact.t()
+  def toggle_flagged_invalid!(contact, flagger \\ nil) do
+    new_state = !contact.flagged_invalid
+
+    attrs =
+      if new_state do
+        %{
+          flagged_invalid: true,
+          flagged_by_user_id: flagger && flagger.id,
+          flagged_at: DateTime.truncate(DateTime.utc_now(), :second)
+        }
+      else
+        # Clear attribution on unflag — the next flag (potentially
+        # by a different admin) gets a fresh record, and the badge
+        # stops claiming a stale flagger after the contact was
+        # restored to valid.
+        %{flagged_invalid: false, flagged_by_user_id: nil, flagged_at: nil}
+      end
+
     contact
-    |> Ecto.Changeset.change(flagged_invalid: !contact.flagged_invalid)
+    |> Ecto.Changeset.change(attrs)
     |> Repo.update!()
   end
 
diff --git a/lib/microwaveprop/radio/contact.ex b/lib/microwaveprop/radio/contact.ex
index aa5bc16b..db6d6bc9 100644
--- a/lib/microwaveprop/radio/contact.ex
+++ b/lib/microwaveprop/radio/contact.ex
@@ -59,6 +59,7 @@ defmodule Microwaveprop.Radio.Contact do
     field :user_submitted, :boolean, default: false
     field :submitter_email, :string
     field :flagged_invalid, :boolean, default: false
+    field :flagged_at, :utc_datetime
     field :private, :boolean, default: false
 
     # Antenna height above ground level (feet). Optional — when set, the
@@ -73,6 +74,7 @@ defmodule Microwaveprop.Radio.Contact do
     field :notes, :string
 
     belongs_to :user, User
+    belongs_to :flagged_by_user, User, foreign_key: :flagged_by_user_id
 
     timestamps(type: :utc_datetime)
   end
diff --git a/lib/microwaveprop_web/live/contact_live/show.ex b/lib/microwaveprop_web/live/contact_live/show.ex
index 0fa817f9..34e979a6 100644
--- a/lib/microwaveprop_web/live/contact_live/show.ex
+++ b/lib/microwaveprop_web/live/contact_live/show.ex
@@ -223,9 +223,24 @@ defmodule MicrowavepropWeb.ContactLive.Show do
     {:noreply, assign(socket, terrain_expanded: !socket.assigns.terrain_expanded)}
   end
 
+  def handle_event("delete_contact", _params, socket) do
+    if admin?(socket.assigns) do
+      Radio.delete_contact!(socket.assigns.contact)
+
+      {:noreply,
+       socket
+       |> put_flash(:info, "Contact deleted.")
+       |> push_navigate(to: ~p"/contacts")}
+    else
+      {:noreply, put_flash(socket, :error, "Admins only.")}
+    end
+  end
+
   def handle_event("toggle_flag", _params, socket) do
     if admin?(socket.assigns) do
-      contact = Radio.toggle_flagged_invalid!(socket.assigns.contact)
+      flagger = socket.assigns.current_scope && socket.assigns.current_scope.user
+      contact = Radio.toggle_flagged_invalid!(socket.assigns.contact, flagger)
+      contact = Microwaveprop.Repo.preload(contact, :flagged_by_user)
       {:noreply, assign(socket, contact: contact)}
     else
       {:noreply, put_flash(socket, :error, "Admins only.")}
@@ -892,7 +907,12 @@ defmodule MicrowavepropWeb.ContactLive.Show do
           <% end %>
           &middot; {Calendar.strftime(@contact.qso_timestamp, "%Y-%m-%d %H:%M UTC")}
           <%= if @contact.flagged_invalid do %>
-            <span class="badge badge-error badge-sm ml-2">Flagged Invalid</span>
+            <span
+              class="badge badge-error badge-sm ml-2 whitespace-nowrap"
+              title={flag_tooltip(@contact)}
+            >
+              Flagged invalid{flag_attribution(@contact)}
+            </span>
           <% end %>
           <%= if @contact.private do %>
             <span
@@ -931,6 +951,14 @@ defmodule MicrowavepropWeb.ContactLive.Show do
             <.icon name="hero-flag" class="w-4 h-4" />
             {if @contact.flagged_invalid, do: "Unflag", else: "Flag as Invalid"}
           </button>
+          <button
+            :if={admin?(assigns)}
+            phx-click="delete_contact"
+            data-confirm={"Permanently delete this contact (#{@contact.station1} / #{@contact.station2})? This cannot be undone."}
+            class="btn btn-sm btn-error btn-outline"
+          >
+            <.icon name="hero-trash" class="w-4 h-4" /> Delete
+          </button>
           <.link navigate={path_calc_url(@contact)} class="btn btn-sm btn-outline">
             <.icon name="hero-calculator" class="w-4 h-4" /> Open in Path Calculator
           </.link>
@@ -2469,6 +2497,25 @@ defmodule MicrowavepropWeb.ContactLive.Show do
   defp maybe_put_band(params, band) when is_binary(band), do: Map.put(params, "band", band)
   defp maybe_put_band(params, _), do: params
 
+  # " by W5XYZ" suffix when we know who flagged it; nothing
+  # otherwise (legacy flags from before the column was added have
+  # `flagged_by_user_id == nil`).
+  defp flag_attribution(%{flagged_by_user: %{callsign: callsign}}) when is_binary(callsign) do
+    " by " <> callsign
+  end
+
+  defp flag_attribution(_), do: ""
+
+  defp flag_tooltip(%{flagged_by_user: %{callsign: callsign}, flagged_at: %DateTime{} = at}) when is_binary(callsign) do
+    "Flagged by #{callsign} on #{Calendar.strftime(at, "%Y-%m-%d %H:%M UTC")}"
+  end
+
+  defp flag_tooltip(%{flagged_at: %DateTime{} = at}) do
+    "Flagged on #{Calendar.strftime(at, "%Y-%m-%d %H:%M UTC")}"
+  end
+
+  defp flag_tooltip(_), do: "Flagged invalid"
+
   attr :grid, :string, default: nil
 
   defp grid_link(assigns) do
diff --git a/priv/repo/migrations/20260504151127_add_flagged_by_user_to_contacts.exs b/priv/repo/migrations/20260504151127_add_flagged_by_user_to_contacts.exs
new file mode 100644
index 00000000..a8d1782d
--- /dev/null
+++ b/priv/repo/migrations/20260504151127_add_flagged_by_user_to_contacts.exs
@@ -0,0 +1,12 @@
+defmodule Microwaveprop.Repo.Migrations.AddFlaggedByUserToContacts do
+  use Ecto.Migration
+
+  def change do
+    alter table(:contacts) do
+      add :flagged_by_user_id, references(:users, type: :binary_id, on_delete: :nilify_all)
+      add :flagged_at, :utc_datetime
+    end
+
+    create index(:contacts, [:flagged_by_user_id])
+  end
+end
diff --git a/test/microwaveprop_web/live/contact_live_test.exs b/test/microwaveprop_web/live/contact_live_test.exs
index 720ea081..dc57ffac 100644
--- a/test/microwaveprop_web/live/contact_live_test.exs
+++ b/test/microwaveprop_web/live/contact_live_test.exs
@@ -974,7 +974,7 @@ defmodule MicrowavepropWeb.ContactLiveTest do
       assert Process.alive?(lv.pid)
     end
 
-    test "flagged_invalid contact shows the Flagged Invalid badge", %{conn: conn} do
+    test "flagged_invalid contact shows the Flagged invalid badge", %{conn: conn} do
       contact = create_contact()
 
       {:ok, contact} =
@@ -983,7 +983,7 @@ defmodule MicrowavepropWeb.ContactLiveTest do
         |> Repo.update()
 
       {:ok, _lv, html} = live(conn, ~p"/contacts/#{contact.id}")
-      assert html =~ "Flagged Invalid"
+      assert html =~ "Flagged invalid"
       # Header station text gets line-through styling when flagged.
       assert html =~ "line-through"
     end