France prop Uini Atonio has been forced to retire after he was admitted to an intensive care unit following a "cardiac event".
The 35-year-old was taken to a hospital in La Rochelle on Tuesday with his club saying he suffered a suspected heart problem, and is now in a stable condition.
"Following his hospitalisation, Uini will have to undergo a long period of recovery," said French Top 14 side La Rochelle, his team since 2011.
Atonio, who was born in New Zealand, qualified to play for France through residency and made 68 appearances for his adoptive country.
During his career the giant prop won the Six Nations Grand Slam in 2022 and was selected for their World Cup squads in 2015 and 2023.
He started all five games as France regained the Six Nations in 2025, and was selected in their provisional squad for this year's tournament.
However, he was withdrawn from the squad earlier this week. It is unclear whether that was for sporting or medical reasons.
"Uini is a wonderful person who really mattered both as a player and as a man within the group," France's forwards coach William Servat said on Wednesday.
"Our thoughts are with his family, his loved ones, his children, his wife - that's what matters today.