William Greig (August 12, 1840 – January 10, 1918) was a farmer, lumber merchant and political figure in Quebec.
He represented Châteauguay in the Legislative Assembly of Quebec from 1892 to 1897 as a Conservative.
He was born in Howick, Lower Canada, the son of William Greig and Janet Brodie, and was educated there.
He was defeated by Joseph-Émery Robidoux when he ran for a seat in the Quebec assembly in 1890.
Greig also ran unsuccessfully for a seat in the House of Commons in 1900.