diff --git a/lib/ecto/adapters/myxql/connection.ex b/lib/ecto/adapters/myxql/connection.ex
index 5165c464..991d6782 100644
--- a/lib/ecto/adapters/myxql/connection.ex
+++ b/lib/ecto/adapters/myxql/connection.ex
@@ -854,6 +854,10 @@ if Code.ensure_loaded?(MyXQL) do
       intersperse_map(columns, ", ", &column_change(table, &1))
     end
 
+    defp column_change(_table, {_command, _name, %Reference{validate: false}, _opts}) do
+      error!(nil, "validate: false on references is not supported in MyXQL")
+    end
+
     defp column_change(table, {:add, name, %Reference{} = ref, opts}) do
       ["ADD ", quote_name(name), ?\s, reference_column_type(ref.type, opts),
        column_options(opts), constraint_expr(ref, table, name)]
diff --git a/lib/ecto/adapters/postgres/connection.ex b/lib/ecto/adapters/postgres/connection.ex
index 187612ae..327e224f 100644
--- a/lib/ecto/adapters/postgres/connection.ex
+++ b/lib/ecto/adapters/postgres/connection.ex
@@ -1121,13 +1121,13 @@ if Code.ensure_loaded?(Postgrex) do
     defp reference_expr(%Reference{} = ref, table, name),
       do: [" CONSTRAINT ", reference_name(ref, table, name), " REFERENCES ",
            quote_table(ref.prefix || table.prefix, ref.table), ?(, quote_name(ref.column), ?),
-           reference_on_delete(ref.on_delete), reference_on_update(ref.on_update)]
+           reference_on_delete(ref.on_delete), reference_on_update(ref.on_update), validate(ref.validate)]
 
     defp constraint_expr(%Reference{} = ref, table, name),
       do: [", ADD CONSTRAINT ", reference_name(ref, table, name), ?\s,
            "FOREIGN KEY (", quote_name(name), ") REFERENCES ",
            quote_table(ref.prefix || table.prefix, ref.table), ?(, quote_name(ref.column), ?),
-           reference_on_delete(ref.on_delete), reference_on_update(ref.on_update)]
+           reference_on_delete(ref.on_delete), reference_on_update(ref.on_update), validate(ref.validate)]
 
     defp drop_constraint_expr(%Reference{} = ref, table, name),
       do: ["DROP CONSTRAINT ", reference_name(ref, table, name), ", "]
@@ -1158,6 +1158,9 @@ if Code.ensure_loaded?(Postgrex) do
     defp reference_on_update(:restrict), do: " ON UPDATE RESTRICT"
     defp reference_on_update(_), do: []
 
+    defp validate(false), do: " NOT VALID"
+    defp validate(_), do: []
+
     ## Helpers
 
     defp get_source(query, sources, ix, source) do
diff --git a/lib/ecto/adapters/tds/connection.ex b/lib/ecto/adapters/tds/connection.ex
index d407327f..861111ef 100644
--- a/lib/ecto/adapters/tds/connection.ex
+++ b/lib/ecto/adapters/tds/connection.ex
@@ -1195,6 +1195,10 @@ if Code.ensure_loaded?(Tds) do
       end
     end
 
+    defp column_change(_statement_prefix, _table, {_command, _name, %Reference{validate: false}, _opts}) do
+      error!(nil, "validate: false on references is not supported in Tds")
+    end
+
     defp column_change(statement_prefix, table, {:add, name, %Reference{} = ref, opts}) do
       [
         [
diff --git a/lib/ecto/migration.ex b/lib/ecto/migration.ex
index 8547c8a4..6ac9b492 100644
--- a/lib/ecto/migration.ex
+++ b/lib/ecto/migration.ex
@@ -370,8 +370,8 @@ defmodule Ecto.Migration do
 
     To define a reference in a migration, see `Ecto.Migration.references/2`.
     """
-    defstruct name: nil, prefix: nil, table: nil, column: :id, type: :bigserial, on_delete: :nothing, on_update: :nothing
-    @type t :: %__MODULE__{table: String.t, prefix: atom | nil, column: atom, type: atom, on_delete: atom, on_update: atom}
+    defstruct name: nil, prefix: nil, table: nil, column: :id, type: :bigserial, on_delete: :nothing, on_update: :nothing, validate: true
+    @type t :: %__MODULE__{table: String.t, prefix: atom | nil, column: atom, type: atom, on_delete: atom, on_update: atom, validate: boolean}
   end
 
   defmodule Constraint do
@@ -1094,6 +1094,9 @@ defmodule Ecto.Migration do
       `:nothing` (default), `:delete_all`, `:nilify_all`, or `:restrict`.
     * `:on_update` - What to do if the referenced entry is updated. May be
       `:nothing` (default), `:update_all`, `:nilify_all`, or `:restrict`.
+    * `:validate` - Whether or not to validate the foreign key constraint on
+       creation or not. Only available in PostgreSQL, and should be followed by
+       a command to validate the foreign key in a following migration if false.
 
   """
   def references(table, opts \\ [])
diff --git a/test/ecto/adapters/myxql_test.exs b/test/ecto/adapters/myxql_test.exs
index 4b5cf2c0..32519136 100644
--- a/test/ecto/adapters/myxql_test.exs
+++ b/test/ecto/adapters/myxql_test.exs
@@ -1283,6 +1283,14 @@ defmodule Ecto.Adapters.MyXQLTest do
     """ |> remove_newlines]
   end
 
+  test "alter table with invalid reference opts" do
+    alter = {:alter, table(:posts), [{:add, :author_id, %Reference{table: :author, validate: false}, []}]}
+
+    assert_raise ArgumentError, "validate: false on references is not supported in MyXQL", fn ->
+      execute_ddl(alter)
+    end
+  end
+
   test "create index" do
     create = {:create, index(:posts, [:category_id, :permalink])}
     assert execute_ddl(create) ==
diff --git a/test/ecto/adapters/postgres_test.exs b/test/ecto/adapters/postgres_test.exs
index 35e6cb82..f069b88e 100644
--- a/test/ecto/adapters/postgres_test.exs
+++ b/test/ecto/adapters/postgres_test.exs
@@ -1435,6 +1435,7 @@ defmodule Ecto.Adapters.PostgresTest do
     alter = {:alter, table(:posts),
              [{:add, :title, :string, [default: "Untitled", size: 100, null: false]},
              {:add, :author_id, %Reference{table: :author}, []},
+             {:add, :category_id, %Reference{table: :categories, validate: false}, []},
              {:add_if_not_exists, :subtitle, :string, [size: 100, null: false]},
              {:add_if_not_exists, :editor_id, %Reference{table: :editor}, []},
              {:modify, :price, :numeric, [precision: 8, scale: 2, null: true]},
@@ -1453,6 +1454,7 @@ defmodule Ecto.Adapters.PostgresTest do
     ALTER TABLE "posts"
     ADD COLUMN "title" varchar(100) DEFAULT 'Untitled' NOT NULL,
     ADD COLUMN "author_id" bigint CONSTRAINT "posts_author_id_fkey" REFERENCES "author"("id"),
+    ADD COLUMN "category_id" bigint CONSTRAINT "posts_category_id_fkey" REFERENCES "categories"("id") NOT VALID,
     ADD COLUMN IF NOT EXISTS "subtitle" varchar(100) NOT NULL,
     ADD COLUMN IF NOT EXISTS "editor_id" bigint CONSTRAINT "posts_editor_id_fkey" REFERENCES "editor"("id"),
     ALTER COLUMN "price" TYPE numeric(8,2),
diff --git a/test/ecto/adapters/tds_test.exs b/test/ecto/adapters/tds_test.exs
index e75e42c6..99d3b6b5 100644
--- a/test/ecto/adapters/tds_test.exs
+++ b/test/ecto/adapters/tds_test.exs
@@ -1214,6 +1214,14 @@ defmodule Ecto.Adapters.TdsTest do
              ]
   end
 
+  test "alter table with invalid reference opts" do
+    alter = {:alter, table(:posts), [{:add, :author_id, %Reference{table: :author, validate: false}, []}]}
+
+    assert_raise ArgumentError, "validate: false on references is not supported in Tds", fn ->
+      execute_ddl(alter)
+    end
+  end
+
   test "create check constraint" do
     create = {:create, constraint(:products, "price_must_be_positive", check: "price > 0")}
 
diff --git a/test/ecto/migration_test.exs b/test/ecto/migration_test.exs
index 0e2ea251..f80a1a52 100644
--- a/test/ecto/migration_test.exs
+++ b/test/ecto/migration_test.exs
@@ -100,6 +100,11 @@ defmodule Ecto.MigrationTest do
            %Reference{table: "posts", column: :id, type: :binary_id}
   end
 
+  test "creates a reference without validating" do
+    assert references(:posts, validate: false) ==
+      %Reference{table: "posts", column: :id, type: :bigserial, validate: false}
+  end
+
   test "creates a constraint" do
     assert constraint(:posts, :price_is_positive, check: "price > 0") ==
            %Constraint{table: "posts", name: :price_is_positive, check: "price > 0"}