Rugby.
According to legend, the game of rugby football was invented at Rugby School in 1823, when a boy named William Webb Ellis, "with a fine disregard for the rules of the game of football as played in his time first took the ball in his arms and ran with it thus originating the distinctive feature of the rugby game". The problem with this is that it is almost certainly untrue in just about every respect.
Nevertheless, the sport of rugby, or Rugby Union, has gone on to become the finest ball sport on earth, as well as spawning the lesser sports of Rugby League and American Football.