Keith Kelvin Deller is an English former professional darts player best known for winning the 1983 BDO World Darts Championship and Unipart British Professional Championship in 1987. He was the first qualifier ever to win the championship and remains one of the youngest champions in history.

His checkout of 138 to clinch the trophy at the 1983 BDO World Darts Championship is amongst the most memorable in darting history. His opponent Eric Bristow had left himself 50 to stay in the match, but decided to throw for single 18 with his last dart to leave double 16 instead of a more difficult attempt at the bullseye. Deller then hit treble 20, treble 18, double 12 for the title, and even to this day commentators often refer to 138 as the "Deller checkout" if a player is left with that score.