Tom Dumoulin (Team Sunweb) placed second, with Thomas's teammate and four-time Tour winner Chris Froome coming third.

The opening stage was won by Fernando Gaviria of Quick-Step Floors, who became the Tour's first rider to wear the general classification leader's yellow jersey.

[1] The average age of riders in the race was 29.37 years,[10] ranging from the 21-year-old Egan Bernal (Team Sky) to the 40-year-old Franco Pellizotti (Bahrain–Merida).

[16] However, Froome's participation was unconfirmed due to an ongoing anti-doping investigation that began in December 2017, when it was announced that he had returned a urine sample taken at the Vuelta (which had taken place two months earlier) which contained twice his allowed amount of the asthma drug salbutamol.

This was considered not as a positive doping result, but as an "Adverse Analytical Finding" (AAF), meaning that he was allowed to continue racing until the case was resolved.

[37] Two weeks after the announcement, the ASO revealed that the Grand Départ would take place over three stages, with the third a team time trial.

[38] In June 2017, the UCI's Professional Cycling Council (PCC) moved the start of the Tour a week later than usual and originally planned due to a clash with the 2018 FIFA World Cup.

[47] The aforementioned, a mountain stage, was the shortest since 1996 and began with a standing start grid formation, with positions based on riders general classification ranking.

The grid formation was an innovation for the Tour, and with shorter distance, was beforehand universally welcomed, but it was thought to have made little effect on the race.

[46] The highest point of elevation in the race was the 2,215 m (7,267 ft)-high Col de Portet Pyrenean pass, the first time it had been used in the Tour.

[47] Stage one's bunch sprint was won by Fernando Gaviria, with Peter Sagan coming in second place and Marcel Kittel in third.

[52] Sagan won stage two from a sprint to take the yellow and green jerseys, with Dion Smith of Wanty–Groupe Gobert claiming the lead in the mountains classification.

[57] In stage six, which ended atop the Mûr-de-Bretagne climb, Dan Martin attacked with a kilometre remaining and was able to stay away take the victory one second ahead of a large group that the contained the general classification contenders.

In the closing kilometres of the stage, Geraint Thomas won a three-second time bonus sprint that brought him to three seconds behind Van Avermaet in the general classification.

In the sprint, André Greipel and Gaviria were penalised for headbutting each other and lost their stage placing and green jersey points.

[47] The first stage in the high mountains and first in the Alps, the tenth, was won by Quick-Step Floors rider Julian Alaphilippe, who attacked on his own with 30 km (18.6 mi) to go from a large breakaway group that included race leader Van Avermaet.

[67] The aforementioned retained the yellow jersey and extended his lead to 2 min 22 s, when pundits predicted the first day in the Alps would be his last as overall race leader.

[67] Thomas achieved back-to-back wins both from the group of overall contenders on stages eleven and twelve by pushing the breakaway riders until the very end.

In the steep summit finish of the eleventh, Thomas attacked in the final 1 kilometre (0.6 miles), passing lone breakaway rider Mikel Nieve (Mitchelton–Scott) and managed to distance himself from Froome and Dumoulin by twenty seconds to take the win.

LottoNL–Jumbo's Steven Kruijswijk was caught by the group of overall contenders in the final kilometres after he had launched a solo attack with 70 km (43.5 mi) remaining.

[71] General classification contender Vincenzo Nibali, who was fourth overall,[72] was forced to withdraw from the Tour following the stage after an incident near the summit of Alpe d'huez where he fell off his bike fracturing a vertebra taking Roglič down with him.

It was initially suspected that the crash had been caused by a police motorcycle driving in front of him, but it later emerged that he became caught in a spectator's camera strap.

[73][74] Nibali's team management saw the lack of crowd control from the police and spectators lighting flares as contributing factors.

[80] Stage fifteen, the start of the final week, was once again a breakaway victory, with Magnus Cort taking Astana's second win in two days.

[82][83] A non-racing incident occurred during the sixteenth stage when hay bales were placed across the road by local farmers protesting about reductions to their subsidies.

[84] After the restart, a large breakaway escaped, and Philippe Gilbert (Quick-Step Floors), while in the lead on a descent, lost control of his bicycle and crashed into and over a wall.

Froome's challenge faded on the approach to the summit of the Col de Portet and he dropped to third position in the general classification, 2 min 31 s behind Thomas.

By this point of the Tour, most of the top sprinters had left, and Démare had come close to missing the time cut in the previous stage along with Sagan, who had crashed heavily and was suffering with injuries.

[98] In addition, there was a combativity award given after each stage to the rider considered, by a jury, to have "made the greatest effort and who demonstrated the best qualities of sportsmanship".

[99] The Souvenir Henri Desgrange, given to first rider to pass the summit of the highest climb in the Tour, the Col du Portet on stage seventeen,[104] and the Souvenir Jacques Goddet, given to the first rider to pass Goddet's memorial at the summit of the Col du Tourmalet in stage nineteen.