Sir William Grant (13 October 1752 – 23 May 1832) was a British lawyer, Member of Parliament from 1790–1812 and Master of the Rolls from 1801–1817.
He was born at Elchies, Moray, Scotland. His father, James Grant, was a tenant farmer, later collector of the customs in the Isle of Man; after the death of his parents, Grant was raised by his uncle Robert Grant, a London merchant with fur-trading interests in Canada. Grant studied at King's College, University of Aberdeen, at the University of Leiden and then studied law at Lincoln's Inn. He was called to the bar in 1774. Grant arrived at the town of Quebec in 1775 and took part in its defence against the Americans. In 1776, he was appointed attorney general for the province. However, Lord George Germain, secretary of state for the American colonies, chose James Monk for the post. In the meantime, Grant had issued ordinances establishing civil and criminal courts in Quebec. He returned to Britain in 1778.
Grant's legal career after his return was initially quite unsuccessful, and he contemplated returning to Canada. However, on the advice of Lord Thurlow, he turned with better success to the equity courts. An interview with Pitt encouraged his Parliamentary ambitions, and he was returned as Member of Parliament for Shaftesbury in 1790. Grant proved to be a powerful orator, giving a lucid explanation of Canadian law during the debates over the Quebec Government Bill.