diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c726e3..7cc2e54 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+### Added
+
+* Add `BitcrowdEcto.Changeset.cast_all/3`, a introspection-based automatic cast function.
+* Add `BitcrowdEcto.Assertions.assert_cast_error_on/2`.
+
 ### Fixed
 
 * Allow any type of `id` param in `Repo.fetch/2`. Remove the (incorrect) guard restricting the `id` param to binaries, against the spec saying it would allow `any`.
diff --git a/lib/bitcrowd_ecto/assertions.ex b/lib/bitcrowd_ecto/assertions.ex
index 31d6499..aa22dd1 100644
--- a/lib/bitcrowd_ecto/assertions.ex
+++ b/lib/bitcrowd_ecto/assertions.ex
@@ -91,7 +91,7 @@ defmodule BitcrowdEcto.Assertions do
     changeset
   end
 
-  for validation <- [:required, :format, :number, :inclusion, :acceptance] do
+  for validation <- [:cast, :required, :format, :number, :inclusion, :acceptance] do
     @doc """
     Asserts that a changeset contains a failed "#{validation}" validation on a given field.
 
diff --git a/lib/bitcrowd_ecto/changeset.ex b/lib/bitcrowd_ecto/changeset.ex
index 001b737..13aca7c 100644
--- a/lib/bitcrowd_ecto/changeset.ex
+++ b/lib/bitcrowd_ecto/changeset.ex
@@ -425,4 +425,120 @@ defmodule BitcrowdEcto.Changeset do
       end
     end
   end
+
+  @type cast_all_option :: {:action, atom}
+
+  @doc """
+  Introspects a schema and casts all defined fields from a params map.
+
+  - Accepts a schema module or structs or changesets.
+  - Can deal with embeds.
+
+  ## Options
+
+  - `required` list of required field names
+  - `optional` list of optional field names (= inverse set is required)
+
+  `required` and `optional` options must not be present at the same time.
+
+  ## Examples
+
+      iex> changeset = cast_all(TestEmbeddedSchema, %{some_field: 4})
+      iex> changeset.valid?
+      true
+
+      iex> changeset = cast_all(%TestEmbeddedSchema{}, %{some_field: 4})
+      iex> changeset.valid?
+      true
+
+      iex> changeset = cast_all(change(%TestEmbeddedSchema{}), %{some_field: 4})
+      iex> changeset.valid?
+      true
+
+      iex> changeset = cast_all(TestEmbeddedSchema, %{}, required: [:some_field])
+      iex> changeset.errors
+      [some_field: {"can't be blank", [validation: :required]}]
+
+      iex> changeset = cast_all(TestEmbeddedSchema, %{}, optional: [:some_other_field])
+      iex> changeset.errors
+      [some_field: {"can't be blank", [validation: :required]}]
+
+  """
+  @doc since: "0.17.0"
+  @spec cast_all(module | struct, map) :: Ecto.Changeset.t()
+  @spec cast_all(module | struct, map, [cast_all_option]) :: Ecto.Changeset.t()
+  def cast_all(schema_or_struct_or_changeset, params, opts \\ [])
+
+  def cast_all(%Ecto.Changeset{} = changeset, params, opts) do
+    do_cast_all(changeset.data.__struct__, changeset, params, opts)
+  end
+
+  def cast_all(schema, params, opts) when is_atom(schema) do
+    do_cast_all(schema, struct!(schema), params, opts)
+  end
+
+  def cast_all(struct, params, opts) when is_struct(struct) do
+    do_cast_all(struct.__struct__, struct, params, opts)
+  end
+
+  defp do_cast_all(schema, struct_or_changeset, params, opts) do
+    required = required_fields(schema, opts)
+    %{scalars: scalars, embeds: embeds} = grouped_fields(schema)
+
+    struct_or_changeset
+    |> cast_scalars(params, scalars, required)
+    |> cast_embeds(embeds, required)
+  end
+
+  defp required_fields(schema, opts) do
+    required = Keyword.get(opts, :required)
+    optional = Keyword.get(opts, :optional)
+
+    cond do
+      required && optional ->
+        raise ArgumentError, ":required and :optional options are mutually exclusive"
+
+      required ->
+        required
+
+      optional ->
+        schema.__schema__(:fields) -- optional
+
+      true ->
+        []
+    end
+  end
+
+  defp grouped_fields(schema) do
+    :fields
+    |> schema.__schema__()
+    |> Enum.group_by(fn field ->
+      case schema.__schema__(:type, field) do
+        {:parameterized, Ecto.Embedded, _} ->
+          :embeds
+
+        # Simplification, can be extended as needed.
+        _other ->
+          :scalars
+      end
+    end)
+    |> Map.put_new(:embeds, [])
+    |> Map.put_new(:scalars, [])
+  end
+
+  defp cast_scalars(schema_struct, params, scalars, required) do
+    # Don't be confused, `--` is right-associative.
+    # https://hexdocs.pm/elixir/1.15.7/operators.html#operator-precedence-and-associativity
+    required = scalars -- scalars -- required
+
+    schema_struct
+    |> Ecto.Changeset.cast(params, scalars)
+    |> Ecto.Changeset.validate_required(required)
+  end
+
+  defp cast_embeds(changeset, embeds, required) do
+    Enum.reduce(embeds, changeset, fn embed, cs ->
+      Ecto.Changeset.cast_embed(cs, embed, required: embed in required)
+    end)
+  end
 end
diff --git a/test/bitcrowd_ecto/assertions_test.exs b/test/bitcrowd_ecto/assertions_test.exs
index a2cfefe..a41c8af 100644
--- a/test/bitcrowd_ecto/assertions_test.exs
+++ b/test/bitcrowd_ecto/assertions_test.exs
@@ -59,6 +59,18 @@ defmodule BitcrowdEcto.AssertionsTest do
     end
   end
 
+  describe "assert_cast_error_on/2" do
+    test "asserts on the :cast error on a field" do
+      cs = changeset(%{some_string: 12, some_integer: 1})
+
+      assert assert_cast_error_on(cs, :some_string) == cs
+
+      assert_raise ExUnit.AssertionError, fn ->
+        assert_cast_error_on(cs, :some_integer)
+      end
+    end
+  end
+
   describe "assert_required_error_on/2" do
     test "asserts on the :required error on a field" do
       cs = changeset() |> validate_required(:some_string)
diff --git a/test/bitcrowd_ecto/changeset_test.exs b/test/bitcrowd_ecto/changeset_test.exs
index d01a51b..3ef9052 100644
--- a/test/bitcrowd_ecto/changeset_test.exs
+++ b/test/bitcrowd_ecto/changeset_test.exs
@@ -5,6 +5,36 @@ defmodule BitcrowdEcto.ChangesetTest do
   import BitcrowdEcto.Assertions
   import BitcrowdEcto.Changeset
 
+  defmodule TestEmbeddedSchema do
+    use Ecto.Schema
+
+    @primary_key false
+
+    embedded_schema do
+      field(:some_field, :integer)
+    end
+
+    def changeset(struct \\ %__MODULE__{}, params) do
+      Ecto.Changeset.cast(struct, params, [:some_field])
+    end
+  end
+
+  defmodule TestVarietySchema do
+    use Ecto.Schema
+
+    @primary_key false
+
+    schema "not_an_actual_table" do
+      field(:some_scalar, :integer)
+      field(:some_enum, Ecto.Enum, values: [:foo, :bar])
+      field(:some_more_complex_scalar, Money.Ecto.Composite.Type)
+      embeds_one(:one_embed, TestEmbeddedSchema)
+      embeds_many(:many_embeds, TestEmbeddedSchema)
+    end
+  end
+
+  doctest BitcrowdEcto.Changeset
+
   describe "validate_transition/3" do
     defp transition_changeset(from, to, transitions) do
       %TestSchema{some_string: from}
@@ -668,4 +698,91 @@ defmodule BitcrowdEcto.ChangesetTest do
       end
     end
   end
+
+  describe "cast_all/3" do
+    defp params do
+      embedded = %{"some_field" => 12}
+
+      %{
+        "some_scalar" => 5,
+        "some_enum" => "foo",
+        "some_more_complex_scalar" => "USD 120",
+        "one_embed" => embedded,
+        "many_embeds" => [embedded, embedded]
+      }
+    end
+
+    test "allows to automatically cast all fields of a schema" do
+      %Ecto.Changeset{} = cs = cast_all(TestVarietySchema, params())
+      assert cs.valid?
+      assert_changes(cs, :some_scalar, 5)
+      assert_changes(cs, :some_enum, :foo)
+      assert_changes(cs, :some_more_complex_scalar, Money.new(:USD, "120"))
+
+      %Ecto.Changeset{} = embedded_cs = cs.changes.one_embed
+      assert embedded_cs.valid?
+      assert_changes(embedded_cs, :some_field, 12)
+
+      assert [%Ecto.Changeset{valid?: true}, %Ecto.Changeset{valid?: true}] =
+               cs.changes.many_embeds
+    end
+
+    test "accepts structs as input" do
+      %Ecto.Changeset{} = cs = cast_all(%TestVarietySchema{}, params())
+      assert cs.valid?
+    end
+
+    test "accepts changesets as input" do
+      %Ecto.Changeset{} = cs = cast_all(change(%TestVarietySchema{}), params())
+      assert cs.valid?
+    end
+
+    test "accepts params maps with atom keys" do
+      cs = cast_all(TestVarietySchema, %{some_scalar: 5})
+      assert cs.valid?
+      assert_changes(cs, :some_scalar, 5)
+    end
+
+    test "returns invalid changeset on cast errors" do
+      cs = cast_all(TestVarietySchema, %{some_scalar: "foo"})
+      refute cs.valid?
+      assert_cast_error_on(cs, :some_scalar)
+    end
+
+    test "accepts a list of required fields and validates them" do
+      cs = cast_all(TestVarietySchema, %{}, required: [:some_scalar])
+      refute cs.valid?
+      assert_required_error_on(cs, :some_scalar)
+      refute_errors_on(cs, :some_enum)
+    end
+
+    test "accepts a list of optional fields and validates them" do
+      cs = cast_all(TestVarietySchema, %{}, optional: [:some_scalar])
+      refute cs.valid?
+      assert_required_error_on(cs, :some_enum)
+      refute_errors_on(cs, :some_scalar)
+    end
+
+    test "required validations work for embeds, too" do
+      cs =
+        cast_all(
+          TestVarietySchema,
+          %{
+            one_embed: nil,
+            many_embeds: []
+          },
+          required: [:one_embed, :many_embeds]
+        )
+
+      refute cs.valid?
+      assert_required_error_on(cs, :one_embed)
+      assert_required_error_on(cs, :many_embeds)
+    end
+
+    test ":required and :optional are mutually exclusive" do
+      assert_raise ArgumentError, ~r/options are mutually exclusive/, fn ->
+        cast_all(TestVarietySchema, %{}, required: [], optional: [])
+      end
+    end
+  end
 end