World number 1 or world no. 1 refers to the highest world ranking in several competitive sports:
List of FIDE chess world number ones, in chess List of PSA women's number 1 ranked players, women's squash List of world number one male golfers, in men's golf List of World Number One female golfers, in women's golf List of world number one snooker players, in snooker World number 1 ranked tennis players, in tennis