The 28-year-old dominated the final, with Spaniard Saul Craviotto Rivero taking silver and Canada’s Mark de Jonge bronze at Eton Dorney.
McKeever crossed the line in 36.246 seconds to win Britain’s second ever Olympic canoe sprint gold medal after Tim Brabants triumphed in 2008.
Speaking to Channel 4 News, he described the final stages of the race:
“Agony from all the lactic acid building and trying to get to the finish line as quickly as possible, and then when I got the finish line the sense of relief and then the joy sunk in.
“I was so proud to be able to do it in front of the British supporters.”
He added: “It is something I will never forget, it’s been an amazing experience, and there’s no reason I can’t get another in four years’ time.”
The Briton adds Olympic gold to his 2010 world and European titles.
McKeever slipped to the third fastest time overall in the semi-finals, behind de Jong and Craviotto Rivero, although only 0.024 seconds separated the trio.
But on finals day, McKeever, who is training to become an accountant, fed off the energy from a cheering 30,000 capacity crowd.