Twice Tour de France champion Alberto Contador is one of six riders to have won all three Grand Tours in a 14-year professional career marred by a doping ban.
Twice Tour de France champion Alberto Contador will hang up his racing bike after this year's Vuelta a Espana, bringing to an end the career of one of the world's greatest cyclists.
The Spaniard, one of six riders to have won all three Grand Tours in a 14-year professional career marred by a doping ban, made his announcement on social media site Instagram on Monday.
"I am retiring from professional cycling. I say this happy and without sadness," the 34-year-old Contador said.
"It's a decision I have thought over very well and I don't think there is a better farewell than in the race in my country. I hope it will be three wonderful weeks."
Nicknamed El Pistolero for his attacking style and ability to mount devastating attacks in the mountains, Contador won his first Tour de France in 2007 with the Discovery Channel team before moving to Astana and winning it again in 2009.
He also won the 2010 edition but in 2012 was stripped of that title after being banned for two years after testing positive for the banned substance clenbuterol at the race.
Contador, who blamed it on contaminated steak, was initially cleared by the Spanish cycling federation but the Court of Arbitration for Sport (CAS) eventually confirmed the ban, backdating it to January 2011.
He returned in 2012 to win the Vuelta.
While Contador, who also stripped of the 2011 Giro d'Italia title, divided opinion within the sport he remained one of the most popular riders among cycling fans.
As well as his Tour triumphs, he won the 2008 and 2015 Giros and the Vuelta in 2008, 2012 and 2014.
In 2015 he announced that he would attempt to become the first rider since Marco Pantani in 1998 to win the Giro and the Tour back-to-back. However, after winning the Italian race his Tour hopes evaporated as he struggled in the Alps and eventually finished fifth.
Contador joined the Trek Segafredo team this season and finished ninth in the Tour de France.