Ben Maher will travel to his first Olympics in the GB show jumping team with Ellen Whitaker missing selection following an injury to her horse.
Maher, 25, joins Whitaker's uncles John and Michael Whitaker in the squad, alongside Tim Stockdale, who will make his first Olympic Games appearance.
Stockdale, 43, sacrificed his hard won place in April's World Cup final to keep his horse fresh for qualification.
Laura Bechtolsheimer, Jane Gregory and Emma Hindle compete in the dressage.
A leg infection to Ellen Whitaker's horse, Locarno 62, ruled her out of the selection process earlier in the week.
Maher said he was unable to believe he had earned a place on the British team.
"Ten months ago my horse, Rolette, was jumping 1.40m national classes and I was having the worst year ever," he said.
"However when she won the Maastricht and Mechelen Grand Prix at the end of last year I knew I had a good horse. She's going from strength to strength and I believe her best is yet to come.
"I am in a state of shock - I never dared to hope we would be in contention for an Olympic team position"
Will Connell, Team GB's equestrian team leader, paid tribute to Maher's recent form.
"Ben has landed some excellent results over the last few months to demonstrate he is ready for his first senior championship team appearance," said Connell.
Maher is joined by fellow debutant Stockdale, 18 years his senior, who withdrew from the World Cup final to keep his horse in peak condition for the outdoor campaign.
Nomination to the Olympic team fulfils an ambition Stockdale has held since he first represented Great Britain in 1988.
"I am over the moon," he told the British Olympic Association's website.
"My mare, Corlato, has gone fantastically well and she deserves the opportunity to jump at the Olympic Games.
"The Olympic Games is everything I have worked for and a huge honour. I am a very lucky man to have such a fantastic horse to ride."
Dressage rider Carl Hester misses out on a fourth Olympic appearance following injuries to his two horses, Lecantos and Dolendo.
Gregory, who is from Great Cheverell in Wiltshire, takes the third place on the dressage team alongside Bechtolsheimer and Hindle.
"I am in a state of shock," she said. "I never dared to hope we would be in contention for an Olympic team position.
"I have ridden Lucky Star since he was four-years-old, he is an extraordinary horse and we are both preparing to give this all we've got."
Dressage team:
Laura Bechtolsheimer riding her own and Dr Wilfried Bechtolsheimer's Mistral Hojris
Jane Gregory riding Greenlands Farm Ltd's Lucky Star
Emma Hindle riding her own Lancet
Reserve: Maria Eilberg riding Ferdi Eilberg's Two Sox
Show jumping team:
Ben Maher riding Mr Daniel Paul's Rolette
Tim Stockdale riding Mr John Bosher's Fresh Direct Corlato
Michael Whitaker riding Gillespie Equestrian's Suncal Portofino 63
John Whitaker riding Miss Rebecca Stones' Peppermill
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