In Canada, the leader of the Opposition in the Senate (French: Chef de l'opposition au Sénat) is the leader of the largest party in the Canadian Senate not in government.

Since senators normally have longer tenure than MPs, this is often the case immediately following a change in government, until the new prime minister can appoint more people from their party.

There are no set rules governing the manner in which the position is filled from within caucuses.

From 1993 until 2003, the leader of the Opposition in the Senate was a Progressive Conservative despite the fact the Progressive Conservatives were not the Official Opposition in the House of Commons; this was because the Official Opposition in the Commons (Bloc Québécois, Reform, Canadian Alliance) did not have Senate representation.

This scenario repeated itself following the results of the 2011 election that saw the Liberal Party lose Official Opposition status in the House to the New Democratic Party, but since the NDP had no representation in the Senate, the Liberals continued to form the Official Opposition in the Senate.