Deep Junior is a computer chess program authored by the Israeli programmers Amir Ban and Shay Bushinsky. Grandmaster Boris Alterman assisted, in particular with the opening book.

Deep Junior won the World Computer Chess Championships in 2002 and 2004, organised by the International Computer Games Association.

In terms of raw power, 'Deep Junior' is dwarfed by other earlier programs such as Deep Blue (which can calculate 200-300 million combinations per second). Deep Junior, which is designed to run on commodity SMP multiprocessor computer hardware, calculates only around 2-3 million combinations per second, but is more selective about the positions it analyzes.

According to Bushinsky, one of the innovations of Deep Junior over other chess programs is its way to count moves. It counts orthodox, ordinary moves as two moves, while an interesting move is one or even less. In this way interesting variations are analysed more deeply than less promising lines. This seems to be a generalization of search extensions already used by other programs.

Another approach they claim to use is 'Opponent modelling'. Deep Junior might play moves which are not objectively the strongest but that play more towards the weaknesses of the opponent.

In 2003 Deep Junior played a 6-game match against Garry Kasparov which resulted in a 3-3 tie.