Turkey's Asli Cakir Alptekin, who won the women's 1500m gold medal at the London Olympics last year, was charged with doping by the International Association of Athletics Federations (IAAF) on Friday.
The 27-year-old has been provisionally suspended after anomalies were discovered in her biological passport.
Her compatriot, Nevin Yanit, the European women's 100m hurdles champion was also suspended after multiple positive dope test results, both in and out of competition, said the IAAF.
"Asli Cakir (Alptekin) and Nevin Yanit have been charged with anti-doping rule violations," IAAF spokesman Nick Davies confirmed to AFP.
"Both cases have been referred to the Turkish Athletic Federation for adjudication as is usual under IAAF rules and we await a decision from them," he added.
If found guilty, Alptekin faces a lifetime ban as it would mark the second time she's fallen foul of anti-doping regulations, having previously a served two-year suspension for a drug offence in 2004.
She would also be stripped of her London Games crown with compatriot Gamze Bulut upgraded to gold, becoming the second athlete to lose her Olympic title after Belarusian shot putter Nadzeya Astapchuk, who tested positive for an anabolic steroid.