A sound card (also known as an audio card) is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs.

Confusingly, the term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware inside the PC. These software-based devices are better known as audio interfaces.

Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation, education, and entertainment (games) and video projection. Many computers have sound capabilities built in, while others require additional expansion cards to provide for audio capability.