Keith Deller (born 24 December 1959 in Ipswich) is an English darts player who won the Embassy World Professional Darts Championship in 1983. He was the first qualifier ever to win the championship and remains one of the youngest champions in history. Deller currently works for Sky Sports as a "spotter" along with Eric Bristow; they use their knowledge and experience to work out for the camera crew where players will be aiming with their next dart.

Deller is also the manager of current PDC World Champion Adrian Lewis.

Deller's victory over Eric Bristow in the tournament by 6 sets to 5 was probably the biggest upset in the history of the championship. He also beat world number 3 John Lowe in the quarter finals and defending champion and world number 2 Jocky Wilson in the semi-final to become the only player in history to defeat the world's top three ranked players in the World Championship. The champion's prize money in 1983 was £8,000.

His checkout of 138 to clinch the trophy is amongst the most memorable in darting history. Bristow had left himself 50 to stay in the match, but decided to throw for single 18 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.