A series of computer software products sold by Sun Microsystems starting in 2003. The products attempt to provide a familiar look and feel on a non-Windows operating system.

The first to be released was a Linux version, which was orignially announced by Sun under the codename Project MadHatter. It includes the SuSE Linux Desktop operating system, but replaces the GUI levels of that product with Sun's versions of the GNOME desktop, Java 2 Standard Edition runtime, StarOffice office suite (StarSuite in Asia), Mozilla web browser, and Evolution e-mail client/PIM.

A Solaris version of the Java Desktop was shipped by Sun in 2004, and is now included in Solaris 10.

The Java Desktop System name has confused some people - it is not named that because the desktop software is written in Java (some of it is, but most was written in C & C++), but the name is instead supposed to signify that it is a desktop system for running Java applications.