diff --git a/core/hash.rbs b/core/hash.rbs
new file mode 100644
index 0000000..bf25e91
--- /dev/null
+++ b/core/hash.rbs
@@ -0,0 +1,45 @@
+class Hash[unchecked out K, unchecked out V] < Object
+  include Enumerable[[K, V]]
+
+  def initialize: () -> void
+
+  def []: %a{implicitly-returns-nil} (K key) -> V
+
+  def []=: (K key, V value) -> V
+
+  def clear: () -> self
+
+  def dup: () -> Hash[K, V]
+
+  def delete: (K key) -> V?
+
+  def empty?: () -> bool
+
+  def has_key?: (K key) -> bool
+
+  def has_value?: (V value) -> bool
+
+  def key: (V value) -> K?
+
+  def keys: () -> Array[K]
+
+  def size: () -> Integer
+
+  alias length size
+
+  alias count size
+
+  def merge: [U, W](Hash[U, W] other) -> Hash[K | U, V | W]
+
+  def merge!: (Hash[K, V] other) -> self
+
+  def values: () -> Array[V]
+
+  def inspect: () -> String
+  def self.inspect: () -> String
+
+  alias to_s inspect
+  alias self.to_s self.inspect
+
+  def each: () { ([K, V]) -> void } -> self
+end
diff --git a/test/hash.rb b/test/hash.rb
new file mode 100644
index 0000000..67c2f6a
--- /dev/null
+++ b/test/hash.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+# rubocop:disable Lint/Void
+# rubocop:disable Style/EmptyLiteral
+# rubocop:disable Style/PreferredHashMethods
+
+hash = { a: 1, b: 2, c: 3 }
+
+Hash.new
+
+hash[:a]
+
+hash[:a] = 2
+
+hash.clear
+
+hash.dup
+
+hash.delete :a
+
+hash.empty?
+
+hash.has_key? :a
+
+hash.has_value? 0
+
+hash.key 2
+
+hash.keys
+
+hash.size
+
+hash.length
+
+hash.count
+
+hash.merge({})
+hash.merge({ 'a' => true, 5 => '' })
+
+hash.merge!({ d: 4 })
+
+hash.values
+
+hash.inspect
+Hash.inspect
+
+hash.to_s
+Hash.to_s
+
+hash.each do |key, value|
+  key
+  value
+end
+
+# rubocop:enable all