• Joomla! 3.x language packs are available here:
Joomla! 3.x Translation Packs •

• Joomla! 2.5 language packs are available here:
Joomla! 2.5 Translation Packs •

• Joomla! 1.5 language packs are available here:
Joomla! 1.5 Translation Packs •

Currently supporting 75 world languages, Joomla! speaks more languages than any other content management system. If your site users speak one language and your administrators another, you can customize your language settings to serve their needs—even on an individual user basis. Whether you speak French, Japanese, or Farsi, Joomla! speaks your language.

All instructions about Joomla! language packs can be found through the links above.