QSound is the original name for a positional three-dimensional (3D) sound processing algorithm from QSound Labs that creates 3D audio effects from multiple monophonic sources and sums the outputs to two channels for presentation over regular stereo speakers. QSound was eventually re-dubbed "Q1" after the introduction of "Q2," a positional 3D algorithm for headphones. As the company's spatial audio algorithm family grew, and multi-speaker surround system support was added to the positional 3D process, the QSound positional 3D audio process became known simply as "Q3D."

The system was used in several Capcom CPS-1 titles and in all CPS-2 and CPS3 titles as well as several console games and the Sony ZN-1 and ZN-2 hardware arcade games such as Battle Arena Toshinden 2.

Electronic Arts, Activision, Microsoft Game Studios, Sega, Virgin Interactive, TDK Mediactive, Bullfrog Productions, and Lionhead Studios have also used the technology, mostly through the use of the QMixer software development kit to implement audio positioning, mixing and control directly in the game software. Later versions of QMixer added support for 3D-accelerated hardware through the low-level Microsoft DirectSound3D Application Programming Interface.

Q3D has been incorporated in a variety of computer sound cards and sound card drivers .

While the system is known by some for its use in video game titles, the first QSound chip used for that purpose was not created until 1991, while QSound had been developed in the late 1980s and has been used in everything from screensavers to television programming. Several 1990s music albums were also "mixed in QSound" (see below) using the QSystem or QSystem II hardware processors, and many other music releases have been enhanced with QSound effects using software plug-in versions of the QSystem and other software utilities. (The QSound website maintains a list of known projects. )

In 2003, Q3D was added to the list of components in QSound Labs' microQ, a small-footprint, performance-optimized software digital audio engine aimed at the mobile market (i.e. cellphones and the like). Q3D enables 3D sound for handheld gaming and can be controlled in Java games via the JSR-234 Application Programming Interface.

It is important to distinguish 3D positional processing from stereo expansion (examples: QSound QXpander, SRS). Positional 3D audio is a producer-side technology. It is applied to individual instruments or sound effects, and is therefore only usable at the mixing phase of music and soundtrack production, or under realtime control of game audio mixing software. Stereo expansion is primarily a consumer-side process that can be arbitrarily applied to stereo content in the end-user environment using analog integrated circuits or digital signal processing (DSP) routines.