William Lock (1 May 1858 – 20 July 1940) was Mayor of Nelson, New Zealand, from 1913 to 1915 and again from 1921 to 1927. Lock was an auctioneer, and a grain and produce merchant for 40 years. During his term as mayor, HMS New Zealand visited Nelson in 1913. Lock died on 20 July 1940 at his home in Collingwood Street, Nelson.