The 25-year-old cleanly beat sprinting royalty in Andre Greipel (Lotto Soudal), Fernando Gaviria (Quick-Step Floors) and Peter Sagan (BORA-hansgrohe) in the flat finish in Amiens.
Gaviria and Greipel were later disqualified after an incident in the final few hundred metres. Gaviria had been boxed in by Greipel in the final 200 metres and the Colombian appeared to headbutt his rival’s lower back in retaliation. Sagan was promoted to second with Degenkolb moved up to third.
Groenewegen has now matched both Gaviria and Sagan at this Tour, each with two wins apiece.
”My shape is getting better by the day, I’m proud that I won again today," Groenewegen said. “Sagan started very early and it was a bit messy, and I surged ahead. It was a good opportunity and I seized it.”
'Compared to last year, I feel more pressure now. The fact that I’m winning the stage here is beyond great. The team did a very good job today and I’m grateful for the confidence that I get from the team.
"I positioned myself in Kristoff’s wheel and with two hundred metres to go I thought: this is the moment. This really gives a lot of confidence for the coming stages.”
The general classification remained unchanged but Greg van Avermaet (BMC) did add a bonus second to his lead over Geraint Thomas (Sky) and Tejay van Garderen (BMC).
Fabien Grellier (Direct Energie) and Marco Minnaard (Wanty-Group Gobert) got on with the business of driving the break on the 181km stage from Dreux to Amiens Métropole to craft a lead of over six minutes.
The stage featured two KOM points, an intermediate sprint and a bonus sprint and as the pair rode on they soaked up the meagre points on offer. Grellier claimed the single point KOMs at the Pacy-sur-Eure and côte de Feuquerolle and bagged 20 contested points at the La Neuve-Grange intermediate sprint.
Behind them, the peloton contested the sprint for the remaining points, with Arnaud Demare (FDJ) beating out Sagan and Gaviria.
The stage continued on placidly with the time gap slowly eroding until the bonus sprint in Loeuilly at kilometre 20, which was won by race leader Greg van Avermaet (BMC) and where the peloton animated.
The increase in intensity forced a crash with 16km to go which claimed a number of riders including Stage 7 winner Dan Martin (UAE Team Emirates) who crashed hard and lost one minute and 15 seconds to his general classification rivals by the finish.
Grellier struck off by himself, but his break ended with 6km to go and the sprinters took over with a 400 metres drag race to the finish which ended with Groenewegen beating Sagan and Gaviria for the second time in two days.
It wasn't a happy day for all the sprinters. In addition to Gaviria and Greipel being relegated, Marcel Kittel (Katusha-Alpecin) vented his rage in the team bus after only finishing 17th on the stage.