Earlier, Marchand – perhaps unsurprisingly – was the fastest qualifier for Friday’s 200m individual medley final, finishing in 1:56.31 after being given another huge reception by the crowd.
Marchand made history on Wednesday with two golds in one night, winning the 200m butterfly title and the 200m backstroke title in the space of two hours.
He also won gold in the 400m medley.
Tom Dean qualified for Friday’s 200m individual medley final in 1:56.92 – but British team-mate Duncan Scott was quicker with 1:56.49.
“It felt all right,” Scott told BBC Sport.
“I probably wanted to be out a bit quicker and work the backstroke a bit more.
“I should have an alright lane for tomorrow night so it should be a good one. I’m excited.”
Elsewhere, Britain’s Ben Proud was the fastest qualifier for Friday’s men’s 50m freestyle final.
Proud clocked 21.38secs to give himself an excellent chance of a first Olympic gold.
The 29-year-old has won world, European and Commonwealth gold in the discipline. but has yet to secure an Olympic medal.
“I have never been in this position – it is very exciting,” Proud told BBC TV.
“It’s funny, not everything went right, but it is about finding that balance of what you can do well and what you can do better.”
Britain’s Honey Osrin was the third-fastest qualifier for the women’s 200m backstroke final in 2:07.84, with Katie Shanahan also reaching the showpiece in 2:08.52.
Britain’s Laura Stephens finished eighth in the women’s 200m butterfly in 2:08.82 – the first final of the night – as Canadian 17-year-old Summer McIntosh set an Olympic record.
McIntosh registered 2:03.03 to claim gold and clinch her third medal in Paris, after triumphing in the women’s 400m medley and taking silver in the 400m freestyle.