On the fourth night of swimming finals at the 2024 Paris Olympics, the heated United States-Australia rivalry takes its latest twist when superstar backstrokers Regan Smith and Kaylee McKeown do battle in a blockbuster women's 100m back final.

Tokyo hero Bobby Finke has a gold medal defense in his sights, French superstar Leon Marchand preps for a busy night, and more in Tuesday's packed night of finals.

Catch the action in Paris beginning at 2:30 p.m. ET on NBC, NBCOlympics.com, Peacock and more.

Women's 100m backstroke final

One of the most anticipated matchups of the Paris swimming program leads off Tuesday's finals when Team USA's Regan Smith takes on Kaylee McKeown of Australia in the women's 100m backstroke.

Together, the pair own the 15 fastest times in the event's history. They've each set two of the four latest world records, with Smith currently holding the mark after swimming 57.13 seconds at June's U.S. Olympic Swimming Trials. McKeown is the defending Olympic champion from Tokyo as well as the 2023 world champion, beating Smith in both, but the American's confidence has never been higher.

The final also features the third- and fourth-fastest women ever in Canada's Kylie Masse (also a former world-record holder) and Team USA's Katherine Berkoff.

La Defense Arena has yet to see a world record fall at these games. If there was ever a race set up to be the first, it's this one.

START LIST

MEDAL FAVORITES:
Regan Smith (USA)
Kaylee McKeown (AUS)
Katherine Berkoff (USA)

THE AMERICANS:
Regan Smith
Katherine Berkoff

Men's 800m freestyle

American distance star Bobby Finke defends his Tokyo gold against a deep field of rivals in the men's 800m free final. 

However, the field will not include the two men who beat Finke at the 2023 World Championships, as Tunisia's Ahmed Hafnaoui is not competing in Paris and Australia's Sam Short finished with the ninth-best time of the prelims, missing out on the final by one spot.

That means Finke's biggest competition will come in the form of Irishman Daniel Wiffen, who set the pace in the prelims, and Italy's Gregorio Paltrinieri, the Tokyo silver medalist and European record holder.

START LIST

MEDAL FAVORITES:
Bobby Finke (USA)
Daniel Wiffen (IRL)
Gregorio Paltrinieri (ITA)

THE AMERICANS:
Bobby Finke
Like Whitlock (DNQ for final)

Men's 4x200m freestyle relay

The United States saw it's four-Games winning streak in this event snapped in Tokyo when it finished fourth, missing a medal entirely. That is unlikely to happen in Paris, though Great Britain is favored to successfully defend its Tokyo gold.

The Brits are led by Matthew Richards and Duncan Scott, who finished second and fourth, respectively, in Monday's men's 200m freestyle final.

The U.S., though, got a promising third-place finish from 21-year-old Luke Hobson, who will likely team up with Chris Guiliano, Drew Kibler and Kieran Smith in hopes of returning Team USA to the podium.

START LIST

MEDAL FAVORITES:
Great Britain
United States
China

THE AMERICANS:
Brooks Curry (relay only)
Chris Guiliano
Luke Hobson
Drew Kibler
Blake Pieroni (relay only)
Kieran Smith

Semifinals

Team USA's young sprint duo, Chris Guiliano and Jack Alexy, race in their first individual Olympic event in the men's 100m freestyle, while Paris double-medalists Torri Huske and Gretchen Walsh return for semis in the women's 100m free.

After winning France's first swimming gold in the men's 400m freestyle, Leon Marchand will look to establish himself as the favorite for gold in two more events, swimming semifinals in the 200m butterfly and 200m breaststroke Tuesday night.