Pidgin (formerly named Gaim) is an open-source multi-platform instant messaging client, based on a library named libpurple. Libpurple has support for many commonly used instant messaging protocols, allowing the user to log into various services from one application.

Pidgin supports multiple operating systems, including Windows as well as many Unix-like systems such as Linux, BSD, Mac OS X, and AmigaOS (through the X11 engine). It has built-in support for NSS, offering client-to-server message encryption for protocols that support it. The program is extendable through plugins, including "Off-the-Record Messaging" and Pidgin encryption, providing end-to-end message encryption.

The following protocols are officially supported by Pidgin, without any extensions or plugins:

• AIM (AOL Instant Messenger)
• Bonjour (Apple's implementation of Zeroconf)
• Gadu-Gadu
• Internet Relay Chat (IRC)
• Lotus Sametime
• MySpaceIM
• MXit
• .NET Messenger Service (commonly known as MSN Messenger or Windows Live Messenger; no multimedia support)
• Novell GroupWise
• OSCAR (AIM/ICQ/.Mac)
• SIMPLE
• SILC
• XMPP (Google Talk, LJ Talk, Gizmo5, Facebook Chat, ...)
• Yahoo! Messenger (only basic chat and file transfers)
• Zephyr