Three of Team USA’s brightest swimming stars chase gold medals on the fourth day of competition from the Tokyo Aquatics Center.
The medal races come thick and fast on Tuesday, with all four finals taking place consecutively, book-ended by a trio of semifinals.
Watch the action LIVE on NBC beginning at 9:30 p.m. ET, or stream the entire session LIVE on NBCOlympics.com and the NBC Sports app.
Women’s 200m Freestyle – Semifinals
Getting out to her usual deceptively pedestrian start, Ariarne Titmus produced a sub-29-second final 50 to win the first semifinal in 1:54.82.
Conversely to Titmus, Ledecky went out strong and led at the 150 mark by nearly a full second in semifinal No. 2. Her time, 1:55.34, was third-fastest overall.
Siobhan Haughey of Hong Kong split the pair, qualifying in second in 1:55.16.
Allison Schmitt, swimming in the first semifinal, finished over two seconds behind Titmus. She missed the final in her fourth Olympics.
Men’s 200m Freestyle – Final
Great Britain's duo of Thomas Dean and Duncan Scott locked out the gold and silver positions, overtaking South Korean flagbearer Hwang Sun-Woo in the final length of the pool.
The margin between the Brits was .04 as Dean won his first Olympic gold medal in 1:44.22.
American Kieran Smith never seriously challenged for the podium, finishing sixth in 1:45.26.
Women’s 100m Backstroke - Final
In a historic final that included three former Olympic record holders and the two previous world record setters, Australian Kaylee McKeown delivered the second fastest time in history, 57.47, to edge out Canada's Kylie Masse and 19-year-old American Regan Smith.
McKeown missed lowering her own world record by .03, settling for the fifth Olympic record set in the event at these very Games.
Masse got out fastest to the 50-meter, turning ahead of world record pace, but could not hold off the Aussie.
Smith, the Lakeville, Minnesota native, took bronze in 58.05, but was never in touching distance of challenging for gold.
The other American competing in the even, Rhyan White swam well to grab the fourth spot.
Men’s 100m Backstroke – Final
It was not to be for Ryan Murphy chasing his second 100m backstroke Olympic gold, as Russian athletes Evgeniy Rylov and Kliment Kolesnikov finished ahead.
Women's 100m Breaststroke – Final
The women's 100m breaststroke gold medal is staying in the U.S., just not the Lower 48.
Alaska's Lydia Jacoby upset not only fellow American Lilly King, but also South African Tatjana Schoenmaker to win gold.
Men’s 200m Butterfly – Semifinal
American Zach Harting faces a star-studded pool of rivals in the first semifinal that features world record holder Kristof Milak of Hungary, Chinese Taipai’s Wang Kuan-Hung and Chad Le Clos of South Africa, gold medal winner in London and silver medallist in Rio.
American Joseph Bentz looks to advance out of the second semifinal.
Women’s 200m Individual Medley – Semifinal
Kate Douglass and Alex Walsh hope to advance out of their respective semifinals. Walsh swims with defending Olympic champion Katinka Hosszu the first semifinal.