Haiku is a free and open-source operating system capable of running applications written for the now-discontinued BeOS, which it is modeled after. Its development began in 2001, and the operating system became self-hosting in 2008. The first alpha release was made in September 2009, and the last was November 2012; the first beta was released in September 2018, followed by beta 2 in June 2020, then beta 3 in July 2021. The fourth beta was released on December 23, 2022, still keeping BeOS 5 compatibility in its x86 32-bit images, with a greatly increased number of modern drivers, GTK3 apps and Wine ported, as well as Xlib (X11) and Wayland compatibility layers.

Haiku is supported by Haiku, Inc., a non-profit organization based in Rochester, New York, United States, founded in 2003 by former project leader Michael Phipps. During the most recent release cycle, Haiku, Inc. employed a developer.