William Gillis (10 November 1859 – 18 September 1929) was a British Labour politician who served as an MP between 1918 and 1922.

Born on a ship in the Black Sea on 10 November 1859, Gillis grew up in Gressenhall in Norfolk.

He was elected to Hoyland Nether Urban District Council and served for a time as its chairman.

He stood in the 1921 Penistone by-election, gaining the seat for Labour, but was defeated at the 1922 general election, and did not stand again.

Following his stint in Parliament, he worked for the YMA and became a magistrate.