His team director told him to go for the win and he finished second on the Mur de Huy behind three-time winner Alejandro Valverde.

[11] After those performances and a string of podium finishes in the Tour de Romandie, Alaphilippe signed a two-year contract extension in May, until the end of the 2017 season.

[12] Later in the month he won the queen stage of the Tour of California, atop Mount Baldy, and took over the lead in the general classification, two seconds ahead of Peter Sagan.

[15] He failed to finish in the road race at the World Championships, and was later diagnosed with infectious mononucleosis – leading to extreme fatigue, and marking the end of his season.

His form continued at the Critérium du Dauphiné where he finished sixth overall and first in the young rider classification – his first white jersey at a UCI World Tour race.

[29] At the World Championships held in Bergen, he broke clear on the last climb of the race and led until under the flamme rouge, before being overhauled by the peloton and finishing tenth.

During the third and final ascent of the Mur de Huy at La Flèche Wallonne, Alaphilippe accelerated near the summit, overtaking Jelle Vanendert in the last 100 metres (330 feet) of the race and dropping him.

It was the biggest victory of Alaphilippe's career at that point, and he was the first French winner of La Flèche Wallonne since Laurent Jalabert won in 1997.

He took the maximum mountains classification points on the Montée du plateau des Glières, the Col de Romme and the Col de la Colombière, finishing the stage to Le Grand-Bornand more than one minute ahead of the second-placed rider Ion Izagirre of Bahrain–Merida, and over three minutes ahead of the peloton that included the defending champion Chris Froome.

[40] The following month, Alaphilippe won the Clásica de San Sebastián, out-sprinting Bauke Mollema for the win, after the two riders escaped the field on the final climb, the Murgil Tontorra.

Despite his large amount of successes in 2018, Alaphilippe faced disappointment at the UCI Road World Championships in Austria, where he was appointed France's team leader.

His first major race was Strade Bianche, which he won on debut, beating out Astana rider Jakob Fuglsang in a kick up the final climb of Via Santa Caterina.

This was followed up by a stage victory in the Tour of the Basque Country,[46] a second place at Brabantse Pijl,[47] a near-miss of a podium place at the Amstel Gold Race,[48] and then three days later, by a successful defence of his La Flèche Wallonne title that he had won in 2018, which made him one of the few riders in history to claim back-to-back victories at the Belgian World Tour race.

Alaphilippe won the third stage of the Tour de France on 8 July, simultaneously earning himself the yellow jersey, after a powerful solo attack inside the last 15 kilometres (9.3 miles).

[52] He then won stage 13, the individual time trial in Pau, by beating Geraint Thomas by 14 seconds on the day that celebrated 100 years since the yellow jersey was created.

[55] Seventh at the Grand Prix Cycliste de Québec in September, he finished his season with a 28th place at the UCI Road World Championships in Yorkshire.

[56][57] At the postponed Tour de France, Alaphilippe won stage 2 in Nice with a powerful sprint from a three-man group that went clear over the final climb of the day, taking the overall lead at the same time.

[58] He held the yellow jersey until stage 5, when he received a 20-second time penalty for taking a bidon inside the final 20 kilometres (12 miles).

[63] On 7 October, Alaphilippe took his first win as World Champion at Brabantse Pijl, ahead of Mathieu van der Poel and Benoît Cosnefroy, with whom he had attacked inside the final 20 kilometres (12 miles).

[65] Alaphilippe started his season by finishing second overall at the Tour de la Provence,[66] before making his debut in Omloop Het Nieuwsblad.

[68] Four days after concluding the race, he made an attack on the Poggio, forcing a selection in the closing kilometres of Milan–San Remo, but eventually finished 16th.

Three days later, he won La Flèche Wallonne for the third time, as he closed down an attack by Primož Roglič 50 metres (160 feet) before the finish; he became the first incumbent world champion since Cadel Evans in 2010 to win the race.

Alaphilippe was part of a five-man group who went clear on the final ascent of the day and managed to hold off the chasers, but was pipped on the line by Tadej Pogačar in the sprint for his second second-place finish at the race.

[78] Alaphilippe made his first move with 58 kilometres (36 miles) to go, attacking on the Flandrien circuit, and bridging with the favourites up to the remaining breakaway riders.