Michael Phelps and Katie Ledecky highlight the swimmers chasing gold medals for the United States on Day 4 of the 2016 Rio Olympics.
In addition to semifinal races whittling down the field for three of Wednesday's finals, four gold medals will be handed out Tuesday night.
Phelps will swim in his signature 200-meter butterfly, likely competing with Hungary's Laszlo Cseh and South Africa's Chad le Clos for the gold. He could join the 800-meter freestyle relay squad, which may include Conor Dwyer and Ryan Lochte.
Ledecky will attempt to secure her second gold and third overall medal of the 2016 Olympics, battling Sarah Sjostrom in the 200-meter freestyle.