Tony Yoka - known as "the French Anthony Joshua" - has been banned from competition for a year by the French anti-doping agency following three no-shows at anti-doping tests between July 2016 and July 2017.
Yoka - a super heavyweight gold medalist at Rio 2016, like Anthony Joshua four years earlier - is often compared to the British champ.
The 26-year-old turned professional straight after the Olympics with the aim of winning the heavyweight world title in the coming years.
The ban is a serious setback for the Frenchman who won his first five professional fights.
"It's a professional mistake. There was negligence on my part, especially after the Olympics," said Yoka. "There has never been any medication taken."