DirectSound is a software component of the DirectX library, supplied by Microsoft, that resides on a computer with the Windows operating system. It provides a direct interface between applications and the sound card drivers on Windows XP and earlier operating systems, enabling applications to produce sounds and music. Besides providing the essential service of passing audio data to the sound card, it provides many needed capabilities such as recording and mixing sound; adding effects to sound e.g. reverb, echo, flange; using hardware controlled buffers for extra speed; positioning sounds in 3D space (3D audio spatialization), capturing sounds from a microphone or other input and controlling capture effects during audio capture. Of these audio mixing and volume control are the most essential.

DirectSound also allows several applications to conveniently share access to the sound card at the same time. Its ability to play sound in 3D added a new dimension to games. It also provides the ability for games to modify a musical script in response to game events in real time, e.g. the beat of the music could quicken as the action heats up.

After many years of development, today DirectSound is a very mature API, and supplies many other useful capabilities, such as the ability to play multichannel sounds at high resolution. While DirectSound was designed to be used by games, a number of professional audio applications now take advantage of its many diverse capabilities.