diff --git a/core/range.rbs b/core/range.rbs
new file mode 100644
index 0000000..b83d58e
--- /dev/null
+++ b/core/range.rbs
@@ -0,0 +1,17 @@
+# FIXME: mruby/c only supports Range[Integer] only
+class Range[out Elem] < Object
+  def ===: (untyped other) -> bool
+  def self.===: (untyped other) -> bool
+
+  def first: () -> Elem
+
+  def last: () -> Elem
+
+  def exclude_end?: () -> bool
+
+  def inspect: () -> String
+  def self.inspect: () -> String
+
+  alias to_s inspect
+  alias self.to_s self.inspect
+end
diff --git a/core/string.rbs b/core/string.rbs
index f114871..fe8142d 100644
--- a/core/string.rbs
+++ b/core/string.rbs
@@ -26,17 +26,15 @@ class String < Object
 
   def <<: (String) -> String
 
-  # TODO: Range
   def slice: (Integer nth) -> String?
            | (Integer nth, Integer len) -> String?
-  #        | (Range range) -> String?
+           | (Range[Integer] range) -> String?
 
   alias [] slice
 
-  # TODO: Range
   def []=: (Integer nth, String val) -> String
          | (Integer nth, Integer len, String val) -> String
-  #      | (Range range, String val) -> String
+         | (Range[Integer] range, String val) -> String
 
   def b: () -> String
 
diff --git a/test/range.rb b/test/range.rb
new file mode 100644
index 0000000..c26d2bc
--- /dev/null
+++ b/test/range.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# rubocop:disable Lint/Void
+# rubocop:disable Style/CaseEquality
+# rubocop:disable Lint/BinaryOperatorWithIdenticalOperands
+
+0..10
+
+(0..10) === (0..10)
+
+(0..10).first
+
+(0..10).last
+
+(0...10).exclude_end?
+
+(0..10).inspect
+Range.inspect
+
+(0..10).to_s
+Range.to_s
+
+# rubocop:enable all
diff --git a/test/string.rb b/test/string.rb
index ae593cd..dbfc076 100644
--- a/test/string.rb
+++ b/test/string.rb
@@ -40,12 +40,15 @@
 
 'abcdef'.slice 2
 'abcdef'.slice 2, 3
+'abcdef'.slice 2..4
 
 'abcdef'[3]
 'abcdef'[3, 3]
+'abcdef'[3...6]
 
 'abcdef'[3] = 'D'
 'abcdef'[3, 3] = 'defghi'
+'abcdef'[3...6] = 'defghi'
 
 'abcdef'.b