John Diefenbaker (1895–1979) was the 13th prime minister of Canada, serving as such from 1957 to 1963.

Diefenbaker may also refer to the following namesakes of the prime minister:

• Diefenbaker the wolf, an animal character in the television series Due South
• Lake Diefenbaker, a Canadian lake
• Saskatoon John G. Diefenbaker International Airport, a Canadian airport

• The Canadian Coast Guard polar icebreaker CCGS Arpatuuq was initially to be named John G. Diefenbaker.