Willoughby Staples Brewster (July 9, 1860 – December 28, 1932) was an Ontario lawyer and political figure.

He represented Brant South in the Legislative Assembly of Ontario from 1908 to 1914 as a Conservative member.

He was born in Haldimand Township, Northumberland County, Canada West, the son of John Brewster, and was educated at Victoria College in Cobourg.

During his time in the assembly, he played an important role in the passing of the Ontario Workmen's Compensation Act.

One of his children, Harold Staples Brewster (1893–1916) was attending Osgood Hall Law School when he joined the Royal Air Corp in May 1915.