Mustang Software, Inc. was a California-based corporation that developed telecommunications software products. Mustang was incorporated in 1988, became a public corporation (NASDAQ ticker symbol MSTG) in 1995. The company was acquired by Quintus Corporation in 2000.

Mustang's first software products were distributed as shareware. As the company grew, it switched to selling through retail channels. Later, Mustang stopped distributing physical products and sold digital licenses for its software.

For most of its lifetime, Mustang's flagship product was Wildcat! BBS. Wildcat! was a bulletin board system that computer users could dial into using a modem to communicate with other users online. Initially, only one user could be dialed into the system at one time, but technological advances later allowed more than one user to be online simultaneously and to interact with one another.

The first versions of Wildcat! were for MS-DOS. In the mid-1990s, Mustang developed a new version called WINServer that for 32-bit Windows.

Wildcat! was sold to Santronics Software, Inc. in 1998 as Mustang wanted to concentrate on its new software products.

Mustang bought Qmodem from The Forbin Project in 1992 and renamed it to Qmodem Pro. Qmodem Pro was an MS-DOS-based communications program, intended for use by computer users to dial into BBS systems.

Mustang developed versions of Qmodem Pro for 16-bit and 32-bit version of Windows. Support for RIP was added in 1993.

Qmodem Pro continued to be sold by Mustang through 2000, and the rights to it were purchased by Quintus.