Hein Verbruggen, the former president of the International Cycling Union, has died at the age of 75.
The Dutchman, who ran the world governing body from 1991 to 2005, had been battling leukemia.
A UCI tweet read: "The UCI is sad to hear about the passing of former President and IOC Member Hein Verbruggen. Our thoughts are with his family and friends."
The UCI is sad to hear about the passing of former President and IOC Member Hein Verbruggen. Our thoughts are with his family and friends pic.twitter.com/oUrYfstWT9— UCI (@UCI_cycling) June 14, 2017
The current UCI president, Brian Cookson, added: "I am sad to hear of the passing of Hein Verbruggen and offer my sincere personal condolences to his family and friends."
Verbruggen's time in charge of the UCI corresponded with a number of controversies.
In 2015, the UCI-supported Independent Commission for Reform in Cycling (CIRC) concluded that, under Verbruggen, the UCI colluded with Lance Armstrong to cover up allegations the seven-times Tour de France winner had doped.
Verbruggen strongly rejected those findings, describing the report as "unfair, biased and incomplete in its methodology, in its substance and in its conclusions".
Cookson had called upon Verbruggen to resign from his position as honorary UCI president in the wake of that report, although the Dutchman declined to do so.
Verbruggen was also a member of the International Olympic Committee from 1996 to 2008, playing a key role in the staging of the Beijing Olympics in 2008.
The IOC said the flag at its headquarters would fly at half-mast as a mark of respect.
"Hein Verbruggen was a fearless fighter for his sport," IOC president Thomas Bach said.
"Thanks to his great engagement and his management skills, he greatly contributed to the success of the Olympic Games Beijing 2008 as chair of the Coordination Commission. For this he will be always remembered."