The list of players heading to Japan includes 17-year-old Gauff, 2021 Australian Open runner-up Brady, Jessica Pegula and Alison Riske for women's singles and Tommy Paul, Frances Tiafoe, Tennys Sandgren and Marcos Giron for men's singles.
Sofia Kenin, the Australian Open champion and French Open runner-up in 2020, is the highest-ranked American woman at No. 6, but she opted not to go to the Olympics.
"That was a difficult decision, but I spoke and discussed that with my agents," Kenin said after losing 6-2, 6-4 to American Madison Brengle in Wimbledon's second round Wednesday. "I couldn't take anyone with me, and I definitely wanted to have someone."
The Tokyo Games were postponed a year ago because of the coronavirus pandemic, and COVID-19 cases are rising in the host city. The Olympics are scheduled to open July 23, less than two weeks after Wimbledon ends.
The International Tennis Federation announced each country's Summer Games entrants for the sport Thursday.
Serena Williams, who is ranked No. 8, ruled herself out over the weekend. She injured her right leg during her match at the All England Club on Tuesday and is out of the tournament.
Brady is No. 15 in the WTA rankings, Gauff -- a quarterfinalist at the French Open this year -- is No. 23, Pegula No. 26 and Riske No. 29.
The first four U.S. men in the ATP rankings -- Reilly Opelka, John Isner, Taylor Fritz and Sebastian Korda -- all decided not to participate in the Olympics, as did the country's sixth-highest man, Sam Querrey. Korda passed up joining golf star sisters Nelly and Jessica Korda in Tokyo.
Instead, this week's rankings of the men signed up for singles are No. 52 Paul, No. 57 Tiafoe, No. 66 Giron and No. 68 Sandgren. Tiafoe beat No. 3 seed Stefanos Tsitsipas, the French Open runner-up, at Wimbledon on Monday.
"It's going to be a different Olympics from years past; it's going to take away from it," Giron said. "That being said, I feel like, as an athlete, I have to go at least once. So when I got the option, I absolutely jumped on it.
"I understand why a lot of the other guys aren't going. But I'm excited and stoked."
Eligibility was based on the rankings of June 14, the day after the French Open ended.
"It's in a pandemic, which will be, probably, not as enjoyable as the past. And I think for American tennis players, it's not a huge priority. It's not as much of a priority as [in] some of the other countries," Querrey said Wednesday after eliminating No. 8 seed Pablo Carreno Busta at Wimbledon. "For most of the Americans, if you play in it, great. But I think for me, I'd rather go play [tour events in] Cabo, Atlanta, D.C. I would rather win Indian Wells than win an Olympic gold, and I think a lot of the other guys feel the same way."
According to the U.S. roster, the rest of its team includes pairings of Gauff with Nicole Melichar and Pegula with Bethanie Mattek-Sands for women's doubles and Tiafoe with Rajeev Ram and Sandgren with Austin Krajicek for men's doubles.
For the Tokyo Paralympics, which are slated to begin Aug. 24, the U.S. tennis team is led by eight-time medalist David Wagner. Also listed are Bryan Barten, Dana Mathewson, Emmy Kaiser, Shelby Baron, Casey Ratzlaff and Conner Stroud.
The Associated Press contributed to this report.