Ruby行内注释的代码在运行时被忽略。单行注释＃字符开始，他们从＃到行末如下：

#!/usr/bin/ruby -w

# This is a single line comment.

puts "Hello, Ruby!"

上述程序执行时，会产生以下结果：

Hello, Ruby!

Ruby的多行注释

可以注释掉多行使用 =begin 和 =end 语法如下:

#!/usr/bin/ruby -w

puts "Hello, Ruby!"

=begin
This is a multiline comment and con spwan as many lines as you
like. But =begin and =end should come in the first line only. 
=end

上述程序执行时，会产生以下结果：

Hello, Ruby!

确保后面的注释是保持足够的距离的代码，能使它很容易区分。如果在一个块中存在一个以上的尾端注释它们对齐。例如：

@counter      # keeps track times page has been hit
@siteCounter  # keeps track of times all pages have been hit