Geraint Thomas is out of the Tour de France after crashing on Sunday's Stage 9 from Nantua to Chambery, Team Sky has announced.
The Welshman suffered a suspected broken collarbone in a crash on the descent of the Col de la Biche, the first of three hors categorie climbs on a day expected to shake up the battle for the yellow jersey.
Team Sky tweeted: "Sadly @GeraintThomas86 has been forced to abandon #TDF2017 following that crash. More updates when we have them."
Thomas began the day second in the general classification, 12 seconds behind his Team Sky teammate Chris Froome, and his exit will come as a major blow for the three-time Tour winner.
It was a fourth crash of the race for Thomas, who spent four days in the yellow jersey after winning the opening time trial in Dusseldorf last weekend.
Thomas had crashed twice while wearing the yellow jersey, on Stages 2 and 4, and on Saturday went straight into a hay bale after he and Froome took a corner too fast on a descent during Stage 8 to Station des Rousses.
The 31-year-old had come into the Tour after his bid to win the Giro d'Italia ended in a crash -- caused by a police motorbike -- on Stage 9 to Blockhaus.
After several days of blazing heat on the Tour, patches of rain came on Sunday to make the descents of this mountainous 181.5-kilometer stage treacherous, with Thomas one of several riders to fall in the early going.