William John Williamson (4 May 1867 – 17 November 1950) was an English-born Australian politician.
He was born in Nantwich to engineer Hugh Christopher Williamson and Emma Cowap, and came to Victoria with his family in 1870.
He attended Melbourne University, graduating in 1892, and was admitted as a solicitor in 1898.
On 21 September 1904 he married Jessie Caroline Nankervis, with whom he had two children.
He served on Portland Borough Council from 1910 to 1922 and was mayor from 1912 to 1913.