The Casio SK-1 is a small sampling keyboard made by Casio in 1985.

It has 32 small sized piano keys, four-note polyphony, with a sampling bit depth of 8 bit PCM and a sample rate of 9.38 kHz, a built-in microphone and line level input for sampling, and an internal speaker. It also features a small number of four-note polyphonic preset analog and digital instrument voices, and a simple additive voice.

All voices may be shaped by 13 preset envelopes, portamento and vibrato. It also includes a rudimentary sequence recorder, preset rhythms and chord accompaniment. The SK-1 was thus an unusually full-featured synth in the sub-$US100 home keyboard market of the time.

The SK-1 has been used by a few major recording artists for its simplicity and lo-fi sound. It became very popular in the late 1990s among the circuit bending crowd after the first guide to bending it was published by Reed Ghazala in Experimental Musical Instruments magazine, though the SK-1 was being modified as early as 1987 when Keyboard Magazine published an article on adding MIDI support. The synthesizer was one of the first pieces of equipment that Autechre had when they began recording music. Musician and score composer Michael Andrews featured a circuit bent SK-1 heavily in the Me and You and Everyone We Know musical score. It was used by notable Jungle artist DJ Hype for his seminal production attempts, as written in book All Crews by Brian Belle-Fortune, and rapper and producer Large Professor used it in his early years of beat-making.

The Radio Shack version of the Casio SK-1 is called the Realistic Concertmate 500. The Casio SK-1 is the predecessor to the Casio SK-5.