11:37 PM ET
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Tonight at the Tokyo Olympics, Australian superstar Ariarne Titmus upset Katie Ledecky in the 400-meter free, seen as Ledecky's toughest race. Men's sprinter Caeleb Dressel earned his first Olympic medal in Tokyo, in the 4x100 relay.

Women's skateboarding will award its first ever Olympic gold. U.S. softball will play against Japan in a preview of what's to come in the gold-medal game later this week. And in the early morning Eastern time on Monday, the U.S. men's gymnastics team will attempt an upset of its own: After a fourth-place finish in qualifications, the Americans will aim for the podium in team finals.

We've got you covered with all the action:

Titmus upsets Ledecky

The highly anticipated showdown between Australia's Ariarne Titmus and five-time Olympic gold medalist Katie Ledecky ended in the slimmest of margins. Ledecky swam her second-fastest time of her career, 3:57.36 -- behind only the world and Olympic record she set at the Rio Olympics -- and still lost to Titmus, who came in at 3:56.69. This is the first time Ledecky has not won gold in an Olympic individual event.

As Titmus touched the wall, her coach was thrilled -- to say the least.

Dressel and U.S. men's relay team win gold

Caeleb Dressel gave the U.S. an early lead in the 4x100-meter freestyle relay. Italy won silver while Australia snatched bronze.

Elsewhere in the pool ...

Regan Smith set an Olympic record in the women's 100-meter backstroke during her semifinal heat.

Taking a breath

After his gold-medal finish in the men's triathlon, all Norway's Kristian Blummenfelt seemed to need was a little rest.

Also in that race, Kevin McDowell came in sixth -- Team USA's best Olympic finish in men's triathlon.