Apache Harmony is a retired open source, free Java implementation, developed by the Apache Software Foundation. It was announced in early May 2005 and on October 25, 2006, the board of directors voted to make Apache Harmony a top-level project. The Harmony project achieved (as of February 2011) 99% completeness for J2SE 5.0, and 97% for Java SE 6. The Android operating system has historically been a major user of Harmony, although since Android Nougat it increasingly relies on OpenJDK libraries.
On October 29, 2011 a vote was started by the project lead Tim Ellison whether to retire the project. The outcome was 20 to 2 in favor, and the project was retired on November 16, 2011.