Lilly King of the U.S. aims to extend her breaststroke dominance.

TOKYO — Lilly King of the United States will take center stage at the Tokyo Aquatics Center on Tuesday morning.

King, 24, who is from Indiana, is brash and outspoken — and dominant in the women’s 100-meter breaststroke. Undefeated at the distance since December 2015 and the current world-record holder, King is the heavy favorite to defend her gold medal from Rio de Janeiro. She would be the first two-time Olympic champion in the event.

The slate of four finals started with the men’s 200-meter freestyle, with Tom Dean and Duncan Scott of Britain taking gold and silver.

The final of the women’s 100-meter backstroke figures to be a scorcher. In three successive heats of opening-round qualifying on Sunday, the Olympic record fell thanks to the handiwork of Kylie Masse of Canada, Regan Smith of the U.S. and, finally, Kaylee McKeown of Australia. On Monday, Smith delivered another message in the semifinals by breaking the record yet again. All three women cruised into the final for their highly anticipated showdown.

And in an Olympic final the U.S. has not lost since 1992, Ryan Murphy will try to keep the tradition going by defending his gold medal in the men’s 100-meter backstroke. He had the fastest time in the semifinals but could be challenged by Kliment Kolesnikov of Russia and Mitch Larkin of Australia. Murphy won both the 100-meter backstroke and the 200-meter backstroke at the 2016 Games.