diff --git a/2021/ruby/.ruby-version b/2021/ruby/.ruby-version
new file mode 100644
index 0000000..00750ed
--- /dev/null
+++ b/2021/ruby/.ruby-version
@@ -0,0 +1 @@
+3
diff --git a/2021/ruby/day_01.rb b/2021/ruby/day_01.rb
new file mode 100644
index 0000000..0448081
--- /dev/null
+++ b/2021/ruby/day_01.rb
@@ -0,0 +1,2 @@
+p ARGF.read.split("\n").map(&:to_i).each_cons(2).count {|x,y| x < y }
+p ARGF.read.split("\n").map(&:to_i).each_cons(3).map(&:sum).each_cons(2).count {|x,y| x < y }