Sir Robert Laird Borden, GCMG PC KC (June 26, 1854 – June 10, 1937) was a Canadian lawyer and politician who served as the eighth prime minister of Canada, in office from 1911 to 1920. He is best known for his leadership of Canada during World War I.

Borden was born in Grand-Pré, Nova Scotia. He worked as a schoolteacher for a period and then served his articles of clerkship at a Halifax law firm. He was called to the bar in 1878, and soon became one of Nova Scotia's most prominent barristers. Borden was elected to the House of Commons of Canada in 1896, representing the Conservative Party. He replaced Charles Tupper as party leader in 1901, and became prime minister after the party's victory at the 1911 federal election.

As prime minister, Borden led Canada through World War I and its immediate aftermath. His government passed the War Measures Act, created the Canadian Expeditionary Force, and eventually introduced compulsory military service, which sparked the 1917 conscription crisis. On the home front, it dealt with the consequences of the Halifax Explosion, introduced women's suffrage for federal elections, and used the North-West Mounted Police to break up the 1919 Winnipeg general strike. For the 1917 federal election (the first in six years), Borden created the Unionist Party, an amalgam of Conservatives and pro-conscription Liberals; his government was re-elected with an overwhelming majority.

Borden retired from politics in 1920, having accepted a knighthood in 1915 – the last Canadian prime minister to be knighted. He was also the last prime minister born before Confederation, and is the most recent Nova Scotian to hold the office. His portrait has appeared on Canadian one hundred-dollar notes produced since 1976, but in late 2016 the government announced Borden's image would be removed during the next redesign.