The Dutchman needed no help from his teammates in the final straight as he slalomed through his rivals to beat German Andre Greipel by almost a bike length after 181km from Dreux, with Colombian Fernando Gaviria crossing the line third.
However, both Gaviria and Greipel were later disqualified. 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.
Slovakia's Peter Sagan was promoted to second, and German John Degenkolb to third. Belgian Greg van Avermaet retained the overall leader's yellow jersey.
“My shape is getting better by the day, I’m proud that I won again today,” said Groenewegen, who won the final stage on the Champs Elysees last year.
“Sagan started very early and it was a bit messy, and I surged ahead. It was a good opportunity and I seized it.”
One of the overall favourites, Ireland’s Dan Martin who won the sixth stage on Thursday, crashed with 17km left and lost one minute 16 seconds.
Martin hit the asphalt as the peloton was speeding up to get ready for the final sprint.
Three of his UAE Emirates team mates dropped back to help him regain his place in the bunch but Martin, with the back of his jersey ripped off and his left elbow bleeding, had to concede time ahead of a crucial ninth stage featuring 21.7km of cobbled sectors.
All the other favourites spent a quiet day in another slow ride.
“It was a good day, no incident, I’m glad I still have the yellow jersey ahead of tomorrow’s stage,” said Van Avermaet, who leads Briton Geraint Thomas by seven seconds.
