Stockfish is a free and open-source chess engine, available for various desktop and mobile platforms. It is developed by Marco Costalba, Joona Kiiski, Gary Linscott, Stéphane Nicolet, and Tord Romstad, with many contributions from a community of open-source developers.

Stockfish is consistently ranked first or near the top of most chess-engine rating lists and is the strongest conventional chess engine in the world. It won the unofficial world computer chess championships in seasons 6 (2014), 9 (2016), 11 (2018), 12 (2018), 13 (2018), 14 (2019), and 16 (2019). It finished runner-up in season 5 (2013), 7 (2014), 8 (2015), and 15 (2019).

Stockfish is derived from Glaurung, an open-source engine by Romstad released in 2004.