Audacious is a free and open-source audio player software with a focus on low resource use, high audio quality, and support for a wide range of audio formats. It is designed primarily for use on POSIX-compatible Unix-like operating systems, with limited support for Microsoft Windows. Audacious was the default audio player in Ubuntu Studio in 2011–12, and was the default music player in Lubuntu until October 2018, when it was replaced with VLC.

Audacious began as a fork of Beep Media Player, which itself is a fork of XMMS. Ariadne "kaniini" Conill decided to fork Beep Media Player after the original development team announced that they were stopping development in order to create a next-generation version called BMPx. According to the Audacious home page, Conill and others "had [their] own ideas about how a player should be designed, which [they] wanted to try in a production environment."

Since version 2.1, Audacious includes both the Winamp-like interface known from previous versions and a new, GTK-based interface known as GTKUI, which resembles foobar2000 to some extent. GTKUI became the default interface in Audacious 2.4.

Before version 3.0, Audacious used the GTK 2.x toolkit by default. Partial support for GTK3 was added in version 2.5, and Audacious 3.0 has full support for GTK3 and uses it by default. However, dissatisfied with the evolution of GTK3, the Audacious team chose to revert to GTK2 starting with the 3.6 release, with long-term plans of porting to Qt.

Since August 8, 2018, GTK3 support was dropped completely.

As of version 4.0, Audacious is using Qt as its primary toolkit but GTK 2.x support is still available.

As of version 4.3, Audacious has reinstated GTK3 support.

Audacious contains built-in gapless playback.