Liam Broady has been selected in the men's singles event at Tokyo 2020 while American Coco Gauff has been forced to withdraw from the women's draw after testing positive for Covid-19.
Broady was offered a spot by the International Tennis Federation based on his world ranking of 141.
The British number five joins Andy and Jamie Murray, Neal Skupski, Joe Salisbury and Heather Watson.
Gauff said she was "so disappointed" at having to pull out of her Games debut.
"It has always been a dream of mine to represent the USA at the Olympics and I hope there will be many more chances for me to make this come true in the future," said the 17-year-old, who is coming off a fourth-round run at Wimbledon.
The Olympics tennis will be missing several high-profile players with Roger Federer, Rafael Nadal, Serena Williams, Victoria Azarenka, Angelique Kerber and Bianca Andreescu all absent.
However, world number ones Novak Djokovic and Ashleigh Barty, both of whom triumphed at Wimbledon earlier this month, intend to play.
As for Broady, Team GB tennis team leader Iain Bates said he was "delighted" the 27-year-old would make his debut appearance at the Games.
"This is brilliant news for Liam," he added. "Thanks to the BOA and ITF for their hard work behind the scenes to ensure that Liam was able to take advantage of this opportunity."
Broady joins a Covid-hit Team GB squad with Dan Evans and Johanna Konta both having withdrawn after testing positive for the virus.
Seven-time Grand Slam doubles winner Jamie Murray, 35, will replace Evans as Skupski's partner in the men's doubles competition.
Earlier on Sunday, Italy's Wimbledon finalist Matteo Berrettini was forced to pull out of the Games with a thigh injury.