On the men's side, Great Britain's two-time defending Olympic champion Andy Murray is headed to Tokyo despite being ranked well outside the top 100 in the world. 2016 silver medalist Juan Martin Del Potro is targeting Tokyo for a comeback from a series of knee injuries. 

Serbia's Novak Djokovic will seek his first Olympic singles gold -- and a calendar Golden Slam -- in this fourth Olympic Games. 

Rio bronze medalist Kei Nishikori will play in front of a home crowd in Tokyo. 

2016 women's singles bronze medalist Petra Kvitova (CZE) it set to compete. 

For the U.S., returners include Rio mixed doubles gold medalist Bethanie Mattek-Sands and Rajeev Ram, who won mixed doubles silver in Rio with Venus Williams.

Four-time Olympic gold medalist Serena Williams, who gave birth to her daughter in September 2017, opted out of going to Tokyo. Williams has twice advanced to the final in pursuit of her first Grand Slam win since having a child, and No. 24 overall. Venus Williams, the most decorated Olympic tennis player in history, is also not going, though she was not mathematically qualified. 

Rio women's singles gold medalist Monica Puig, who entered those games unseeded and won Puerto Rico's first Olympic gold, will miss the Tokyo Games after undergoing shoulder surgery. Germany's 2016 silver medalist Angelique Kerber also opted out to nurse an injury.

Switzerland's Roger Federer will not pursue the Olympic singles title that's eluded him through four berths so far -- he missed Rio because of a knee injury, and is also dealing with knee injury now. Spain's Rafael Nadal also opted out of the Games. 

Russia's Ekaterina Makarova, who won the 2016 women's double title along with Elena Vesnina, retired in 2020. London 2012 men's doubles champions Bob and Mike Bryan, who withdrew from Rio over health concerns, also retired last year.

Technically a new star since Rio, although she's already a household name, Japan's Naomi Osaka is shaping up to be one of the biggest names at her home Olympics. Osaka has picked up four Grand Slam titles since 2018, become a near-universal fan favorite, and was one of the highest-earning athletes in the world in 2020.

All of the United States' singles qualifiers are heading to their first Olympics. 

Former UCLA player Jennifer Brady is the highest-ranked female qualifier for U.S., having somewhat recently made the rare jump from college to professional success and making her first major final at the 2021 Australian Open (where she lost to Osaka). Teenage phenom Coco Gauff, 17, was also set to go to Tokyo, but tested positive for COVID-19. Jessica Pegula and Alison Riske are rounding out the women's singles roster. 

On the U.S. men's side, the thee highest-ranked men opted out of the Games. Tommy Paul, Frances Tiafoe, Tennys Sandgren and Marcos Giron are now all set to make their Olympic debuts (Paul is the only one who qualified outright).

Australia's Ashleigh Barty, the current World No. 1, is set to complete. 

Russia's Daniil Medvedev, who's made two major finals in the last two years, intends to play in Tokyo. Greece's Stefanos Tsitsipas, who made his first ATP final in 2018, also plans to play.