JRuby is an implementation of a Ruby interpreter in Java. JRuby allows the interaction of Java and Ruby in both directions. This JRuby allows the use of Ruby as an alternative language for the Java runtime environment, such as BeanShell, Groovy or Jython.

JRuby was originally started in 2001 by Jan Arne Petersen, 2008, Charles Nutter, Thomas Enebo, Ola Bini and Nick Sieger main developers.

The Ruby implementation is for Ruby on Rails sufficiently close to the original, a few features of Ruby are not yet supported, including continuations.

Since late September 2007, in addition to the JRuby interpreter contains a compiler which translates Ruby 1.8 classes into Java classes.

On February 24, 2009, succeeded Charles Nutter JRuby on the Android platform up and running on. This project was continued in 2010 under the name Ruboto during initiated by Google " Summer of Code " by Daniel Jackoway.