Katie Ledecky takes center stage on the pool deck Sunday, chasing her first of what could be several gold medals at the Tokyo Olympics.

Ledecky will race the final of the women’s 400m freestyle, one of the three events in which she is both the world record holder and the defending Olympic gold medalist.

This time, though, gold is far from a foregone conclusion. Australian Ariarne Titmus, competing in her first Olympics, boasts the fastest time in the world in 2021. She also knows how it feels to beat Ledecky in a major championship, outtouching the American superstar in the 400 free final at 2019 Worlds.

Elsewhere, Caeleb Dressel, Team USA’s top male star, will take his first strokes in Tokyo as part of the men’s 4x100m freestyle relay. Italy, Australia and France all pose threats to the U.S. in the event the Americans won in 2016 and, most memorably, at Beijing 2008.

Adam Peaty, the world record holder and defending Olympic champion in the men’s 100m breaststroke, is the most dominant swimmer in any individual event not named Katie Ledecky. It should be academic for Peaty in the event’s final, while Americans Andrew Wilson and Michael Andrew hold outside shots at a podium place.

The women’s 100m butterfly final, leading off the session, is wide open with the top six swimmers, including American teenager Torri Huske, qualifying within three fourths of a second of each other.

In one of the evening’s four event semifinals, the women’s 100m backstroke will be on record watch after Kylie Masse, Regan Smith and Kaylee McKeown broke Olympic records in back-to-back-to-back heats.

Each day’s swimming finals are airing LIVE as part of NBC’s signature primetime Olympics coverage. Sunday’s session can also be streamed on NBCOlympics.com and the NBC Sports app.