The 1971 New Democratic Party leadership election was a leadership convention held in Ottawa from April 21 to 24 to elect a leader of the New Democratic Party of Canada. Tommy Douglas retired as federal leader, and David Lewis was elected as his successor. At this convention the Waffle faction was at the zenith of its popularity and power. Donald C. MacDonald, the former Ontario NDP leader, was elected as the party's president. The major non-leadership issues were what stance would the party take in terms of Quebec sovereignty and whether policy initiatives calling for the nationalization of the oil, gas, and mining industries would pass.

The New Democratic Party is a federal political party in Canada. Widely described as social democratic, the party occupies the centre-left of the political spectrum, with the party generally sitting to the left of the Liberal Party. The party was founded in 1961 by the Co-operative Commonwealth Federation (CCF) and the Canadian Labour Congress (CLC).