diff --git a/lib/gc_index_relay/nostr.ex b/lib/gc_index_relay/nostr.ex
index edd257b..1ab2725 100644
--- a/lib/gc_index_relay/nostr.ex
+++ b/lib/gc_index_relay/nostr.ex
@@ -12,6 +12,7 @@ defmodule GcIndexRelay.Nostr do
   import Ecto.Query, warn: false
   alias GcIndexRelay.Nostr.Validator
   alias GcIndexRelay.Nostr.PubEvent
+  alias GcIndexRelay.Nostr.Filter
   alias GcIndexRelay.Repo
   alias GcIndexRelay.Nostr.Event
 
@@ -28,6 +29,26 @@ defmodule GcIndexRelay.Nostr do
     |> PubEvent.from_db()
   end
 
+  @doc """
+  Queries Nostr events using a NIP-01 filter.
+
+  Returns a list of `GcIndexRelay.Nostr.PubEvent` structs matching the filter criteria.
+  """
+  @spec query_events(map()) :: {:ok, [PubEvent.t()]} | {:error, String.t()}
+  def query_events(filter_map) when is_map(filter_map) do
+    with {:ok, filter} <- Filter.from_map(filter_map),
+         events <-
+           from(e in Event)
+           |> Filter.apply(filter),
+         pub_events <-
+           Enum.map(events, fn event ->
+             {:ok, pub_event} = PubEvent.from_db(event)
+             pub_event
+           end) do
+      {:ok, pub_events}
+    end
+  end
+
   @doc """
   Writes a `GcIndexRelay.Nostr.PubEvent` to the database.
   """
diff --git a/lib/gc_index_relay_web/controllers/fallback_controller.ex b/lib/gc_index_relay_web/controllers/fallback_controller.ex
index b980357..44b8aa8 100644
--- a/lib/gc_index_relay_web/controllers/fallback_controller.ex
+++ b/lib/gc_index_relay_web/controllers/fallback_controller.ex
@@ -14,6 +14,13 @@ defmodule GcIndexRelayWeb.FallbackController do
     |> render(:error, changeset: changeset)
   end
 
+  # This clause handles string error messages (e.g., from filter validation).
+  def call(conn, {:error, message}) when is_binary(message) do
+    conn
+    |> put_status(:bad_request)
+    |> json(%{errors: %{detail: message}})
+  end
+
   # This clause is an example of how to handle resources that cannot be found.
   def call(conn, {:error, :not_found}) do
     conn
diff --git a/lib/gc_index_relay_web/controllers/filter_controller.ex b/lib/gc_index_relay_web/controllers/filter_controller.ex
new file mode 100644
index 0000000..af6786d
--- /dev/null
+++ b/lib/gc_index_relay_web/controllers/filter_controller.ex
@@ -0,0 +1,133 @@
+defmodule GcIndexRelayWeb.FilterController do
+  use GcIndexRelayWeb, :controller
+
+  alias GcIndexRelay.Nostr
+
+  action_fallback GcIndexRelayWeb.FallbackController
+
+  @doc """
+  GET /api/events - Query events by specifying NIP-01 filter parameters in the URL query string.
+
+  # Required Parameters
+
+  The `since`, `until`, and `limit` parameters are required. This ensures every query generates a
+  unique, repeatable response. Queries that do not specify `since`, `until`, or `limit` should be
+  made against POST /api/events/filter.
+  """
+  def index(conn, params) do
+    with {:ok, filter_map} <- parse_query_params(params),
+         {:ok, events} <- Nostr.query_events(filter_map) do
+      render(conn, :index, events: events)
+    end
+  end
+
+  @doc """
+  POST /api/events/filter - Query events using a JSON filter in the request body.
+  """
+  def query(conn, filter_params) do
+    with {:ok, events} <- Nostr.query_events(filter_params) do
+      render(conn, :index, events: events)
+    end
+  end
+
+  # Parse query parameters into a NIP-01 filter map
+  @spec parse_query_params(map()) :: {:ok, map()} | {:error, String.t()}
+  defp parse_query_params(params) do
+    # Require since, until, and limit for client-side caching and predictable pagination
+    with :ok <- require_param(params, "since"),
+         :ok <- require_param(params, "until"),
+         :ok <- require_param(params, "limit"),
+         {:ok, recognized_params} <- validate_known_params(params) do
+      parse_params(recognized_params)
+    end
+  end
+
+  # Ensure a required parameter is present
+  @spec require_param(map(), String.t()) :: :ok | {:error, String.t()}
+  defp require_param(params, key) do
+    if Map.has_key?(params, key) do
+      :ok
+    else
+      {:error, "Missing required parameter: '#{key}'"}
+    end
+  end
+
+  # Validate that only known NIP-01 filter keys are present
+  @spec validate_known_params(map()) :: {:ok, map()} | {:error, String.t()}
+  defp validate_known_params(params) do
+    known_keys = ["ids", "authors", "kinds", "since", "until", "limit"]
+
+    unknown_keys =
+      params
+      |> Map.keys()
+      |> Enum.reject(fn key ->
+        key in known_keys or String.starts_with?(key, "#")
+      end)
+
+    case unknown_keys do
+      [] -> {:ok, params}
+      [key | _] -> {:error, "Unknown query parameter: '#{key}'"}
+    end
+  end
+
+  # Parse individual parameters from strings to proper types
+  @spec parse_params(map()) :: {:ok, map()} | {:error, String.t()}
+  defp parse_params(params) do
+    result =
+      params
+      |> Enum.reduce_while({:ok, %{}}, fn {key, value}, {:ok, acc} ->
+        case parse_param(key, value) do
+          {:ok, parsed_value} -> {:cont, {:ok, Map.put(acc, key, parsed_value)}}
+          {:error, _} = error -> {:halt, error}
+        end
+      end)
+
+    result
+  end
+
+  # Parse individual parameter based on its key
+  @spec parse_param(String.t(), String.t()) :: {:ok, any()} | {:error, String.t()}
+  defp parse_param("ids", value), do: {:ok, String.split(value, ",")}
+  defp parse_param("authors", value), do: {:ok, String.split(value, ",")}
+
+  defp parse_param("kinds", value) do
+    value
+    |> String.split(",")
+    |> Enum.reduce_while({:ok, []}, fn kind_str, {:ok, acc} ->
+      case Integer.parse(kind_str) do
+        {kind, ""} -> {:cont, {:ok, [kind | acc]}}
+        _ -> {:halt, {:error, "Invalid kind value: '#{kind_str}' must be an integer"}}
+      end
+    end)
+    |> case do
+      {:ok, kinds} -> {:ok, Enum.reverse(kinds)}
+      error -> error
+    end
+  end
+
+  defp parse_param("since", value) do
+    case Integer.parse(value) do
+      {int, ""} -> {:ok, int}
+      _ -> {:error, "Invalid since value: '#{value}' must be an integer"}
+    end
+  end
+
+  defp parse_param("until", value) do
+    case Integer.parse(value) do
+      {int, ""} -> {:ok, int}
+      _ -> {:error, "Invalid until value: '#{value}' must be an integer"}
+    end
+  end
+
+  defp parse_param("limit", value) do
+    case Integer.parse(value) do
+      {int, ""} -> {:ok, int}
+      _ -> {:error, "Invalid limit value: '#{value}' must be an integer"}
+    end
+  end
+
+  # Handle tag parameters (keys starting with "#")
+  defp parse_param("#" <> _tag_name, value) do
+    {:ok, String.split(value, ",")}
+  end
+end
diff --git a/lib/gc_index_relay_web/controllers/filter_json.ex b/lib/gc_index_relay_web/controllers/filter_json.ex
new file mode 100644
index 0000000..d96711a
--- /dev/null
+++ b/lib/gc_index_relay_web/controllers/filter_json.ex
@@ -0,0 +1,22 @@
+defmodule GcIndexRelayWeb.FilterJSON do
+  alias GcIndexRelay.Nostr.PubEvent
+
+  @doc """
+  Renders a list of events.
+  """
+  def index(%{events: events}) do
+    %{data: Enum.map(events, &data/1)}
+  end
+
+  defp data(%PubEvent{} = event) do
+    %{
+      id: event.id,
+      pubkey: event.pubkey,
+      created_at: event.created_at,
+      kind: event.kind,
+      content: event.content,
+      sig: event.sig,
+      tags: event.tags
+    }
+  end
+end
diff --git a/lib/gc_index_relay_web/router.ex b/lib/gc_index_relay_web/router.ex
index 36d4d05..9e3bbb0 100644
--- a/lib/gc_index_relay_web/router.ex
+++ b/lib/gc_index_relay_web/router.ex
@@ -23,6 +23,8 @@ defmodule GcIndexRelayWeb.Router do
   scope "/api", GcIndexRelayWeb do
     pipe_through :api
 
+    get "/events", FilterController, :index
+    post "/events/filter", FilterController, :query
     resources "/events", EventController, only: [:show, :create, :delete]
   end