After Cha had broken the Olympic record in a blistering lap, the ice-cool Lorentzen went 0.01 seconds faster, zooming around the track in a time of 34.41. Chinese Gao Tingyu took the bronze medal.
Lorentzen was the first Norwegian to win the Olympic 500m title since Finn Helgesen 70 years ago and he became his country’s first medallist in the event since Magne Thomassen won silver in 1968.
Racing in the 14th pair, Cha stormed out of the gates to send the crowd wild and the Korean brought the house down when he crossed in record time with eight racers to come.
Lorentzen, who was in the third-last pair alongside Sochi bronze medallist Ronald Mulder of the Netherlands, was behind Cha after the first 100 metres, but edged in front over the finish line.
He ended with a flurry of effort, his arms and legs pumping like pistons, before waiting nervously until the timekeepers put his name up on the big screen.