Swimmer Tom Gallagher has delivered the first gold medal of his career and Australia's first of the 2024 Paris Paralympics.

Gallagher powered home through the final throes of the men's S10 50m freestyle final at a packed-out La Defense Arena to snatch first place.

The 25-year-old's surge down the home stretch ensured he held off a chasing pack that included Australian teammate Rowan Crothers, who finished with bronze.

"Being the first gold medal of the comp means so much for me," Gallagher said.

"In Tokyo I was a different athlete, I had a lot of medical issues in my pancreas, so after the 400m, I ended up in hospital for about a month and nearly died.

"I luckily had a surgery a few years ago now that's fixed it all and I've managed to turn into a sprinter.

"Pancreatitis is extremely painful, my heart rate went up to 240bpm and all my internal organs started shutting down.

"I wasn't able to go on the podium that night but tonight makes up for it."

Gallagher and Crothers's medals helped put a shine on an afternoon that began with a bang.

Earlier, Brenden Hall and Lakeisha Patterson claimed Australia's first two Paralympic medals in the space of 10 minutes.

Hall clinched his seventh Paralympic medal with bronze in the men's S9 400m freestyle on Friday morning, AEST, at a packed-out La Defense Arena in Paris.

Patterson had led her S9 400m freestyle race right up until the final lap where she was pipped to gold by Hungary's Zsofia Konkoly and had to settle for silver.

"I could see her closing in that last 200 and I like a chase and thought I'd be able to get there tonight," Patterson said.

"I certainly can't complain, it's my third Paralympics now and I've podiumed at all three Games and that's a special feeling."

Hall, meanwhile, made a late dash to claim bronze after missing out on medals at Tokyo.

The 31-year-old's race was made all the more dramatic by French local Ugo Didier surging past Italy's Simone Barlaam on the final stretch to claim gold.

"I was after a little bit of redemption, and I just wanted to come back with a medal this time," Hall said.

"I didn't care what colour it was and so to be able to do it in front of people who mean the most to me, that's what made me feel it the most."

Alexa Leary, who earlier on Thursday set a world record that was bettered in just 10 minutes, finished sixth in the women's S10 50m freestyle.

Ben Hance had to settle for fourth in the men's S14 100m butterfly, while Paige Leonhardt placed seventh in the women's S14 100m butterfly.

AAP