Gravis Ultrasound or GUS is a sound card for the IBM PC compatible system platform, made by Canada-based Advanced Gravis Computer Technology Ltd. It was very popular in the demo scene in the 1990s, due to its superior sound quality compared to similarly-priced soundcards of its time.

The Gravis Ultrasound was unique at the time of its launch (1992) with its use of 'wavetable' sample-based music synthesis technology on the IBM PC platform — the ability to use real-world sound recordings rather than artificial computer-generated waveforms to base a musical instrument on; so a piano sounds like an actual real piano, a trumpet like an actual trumpet, etc. The GUS was remarkable for MIDI playback quality with a large set of instrument patches that could be stored in its own RAM, having up to 32 hardware audio channels of audio.

The cards (all manufactured on red PCBs, similar to fellow Canadian company ATI) were very agreeably priced, although a little more expensive than Creative cards; they undercut many equivalent professional cards aimed at musicians by a huge margin, and brought CD quality audio reproduction within the grasp of home PC users.

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