McKeever justified his nickname of "Usain Bolt on Water" by powering to victory in 36.246 seconds in the sport's fastest and newest Olympic discipline. He had the best start in the eight-man field and comfortably held on in a fierce headwind at Dorney Lake.
Saul Craviotto Rivero of Spain won the silver medal, 0.25 seconds behind. Mark de Jonge took the bronze despite a poor start for Canada's third medal of the regatta.
McKeever was the 200 world champion in 2010, before losing the title to Poland's Piotr Siemionowski. Siemionowski surprisingly failed to reach the Olympic final after finishing sixth in his semifinal.
McKeever is the second Briton to win Olympic gold in the sprint, following Tim Brabants in the K-1 1,000 in Beijing in 2008.
Craviotto Rivero won his second Olympic medal, his first coming in the discontinued 500-meter K-2 in Beijing. De Jonge's spot at the Olympics had been in jeopardy after he dropped an 80-pound dumbbell on his hand in April, breaking his left middle finger three weeks before Canadian trials. His federation delayed the trials until June.