William Rigg (7 May 1847 – 3 November 1926) was an English-born Australian politician.

He was born in Liverpool to joiner George Rigg and Sarah Barclay.

The family moved to New South Wales around 1852, and Rigg attended Christ Church School until the age of fifteen, when he began working in the office of the Illawarra Steam Navigation Company.

He was six times Mayor of Newtown and served as an alderman for twenty-three years.

In 1894 Rigg was elected to the New South Wales Legislative Assembly as the member for Newtown-St Peters; he was generally considered a Free Trader.