Michael Phelps left the Maracana stadium early on Friday after bearing the US flag at the Olympic Games opening ceremony.
The 31-year-old returned to the Olympic village ahead of his teammates to prepare for the Rio 2016 swimming program, which was due to begin on Saturday.
It was the first time Phelps has participated in an Olympic opening ceremony. He has avoided taking part at previous Games to focus on his events, which usually begin the next day.
Phelps was just the second swimmer to carry the US flag, joining four-time Olympic medalist Gary Hall, who was given the honor at the Montreal Games in 1976.
In Rio, Phelps will compete in the 100m and 200m butterfly and 200m individual medley. He is also expected to be a part of the USA relay teams.
In addition to adding to his Olympic medal tally, Phelps is aiming to become only the third athlete to win gold in the same event at four consecutive Olympics, joining Al Oerter (discuss) and Carl Lewis (long jump). He could perform the feat in both the 100m butterfly and 200m individual medley.
