OXO was a computer game developed by Alexander S. Douglas in 1952 for the EDSAC computer, which simulates a game of Noughts and crosses, also sometimes called Tic-tac-toe. OXO is the earliest known game to display visuals on a video monitor.

To play OXO, the player would enter input using a rotary telephone controller, and output was displayed on the computer's 35×16 dot matrix cathode ray tube. Each game was played against an artificially intelligent opponent.