Now France's Michael Phelps – he is trained by Phelps' mentor Bob Bowman – has taken three Olympic Games gold medals and can take another one.
Marchand started the Olympic Games by winning his safest distance, the 400 meter medley world record event.
On 200 meter butterfly, many thought he would have it toughest since Hungarian world record holder and reigning Olympic champion Kristof Milak had looked sharp.
But driven by nearly 15,000 people in a boiling Paris La Defense Arena, he defeated Milak by a little over half a second and won with a new Olympic record of 1.51,21.
On 200 meter breaststroke, he struck again with another Olympic record, 2.05,85 – just 37 hundredths above Chinese Qin Haiyang's world record.
Again, he defeated the reigning champion, Australia's Zac Stubblety-Cook, who was 94 hundredths behind.
Leon Marchand can take a fourth gold when the 200 meter medley starts on Thursday.
Chinese Pan Zhanle set the first world record in Olympic swimming. Pan won 100 meter freestyle and broke his own world record by four tenths to 46,40.
He won the gold medal convincingly, a little over a second ahead of Kyle Chalmers, Australia.