William Leggat Ritchie (1884 – 12 February 1966) was a Scottish professional golfer.

His most successful year was 1910 when he tied for 16th place in the Open Championship and won the Perrier Water Assistant Professionals' Tournament.

Ritchie's best season was 1910 while he was an assistant to James Braid at Walton Heath Golf Club.

Later in the year Ritchie won the first Perrier Water Assistant Professionals' Tournament at Bushey Hall Golf Club.

The prizes for this tournament were "presented by the proprietors of Perrier Water", the winner receiving 20 guineas (£21) and a gold watch.