William Benjamin Chaffey, CMG (21 October 1856 – 4 June 1926) was a Canadian engineer and irrigation planner who with his older brother George Chaffey developed what became the cities of Etiwanda, California, Ontario, California, and Upland, California in the United States of America, as well as the cities of Mildura, Victoria and the town of Renmark, South Australia, in Australia.