The 213.5-kilometre flat route from Reims to Nancy did not pose any major difficulty and was a ideal opportunity for sprinters to get a stage win, a day after Viviani's teammate Julian Alaphilippe seized the yellow jersey with a solo effort.
"This means a lot and I still can't believe it", said Viviani at the end of the stage. It was a big goal of the year.
Viviani's decision to quit May's Giro d'Italia, despite a lack of success, in order to save himself for the sprint stages of the Tour, was vindicated as he powered clear of Alexander Kristoff of Norway to take a career-first stage win in the Tour. "I just really focused on my lead out, because I lost the wheel of my lead out in the first stage and I was really disappointed after that", Viviani explained.
"My father and mother were on the finish line today, they were set to leave yesterday but finally chose to stay because the stage was for sprinters", Viviani said.
"What a handsome way to start the tour here in France", he said.
Julian Alaphilippe is the new leader of this year's Tour de France following victory on stage 3 into Épernay. Italian Viviani triumphed in the first pure sprint opportunity of the Tour after the uphill effort in Brussels on the opening day.
"I said today "I will only focus on Max Richeze's wheel", I know Morkov does an unbelievable job, he is the best in choosing the time and he did it perfectly today".
The 213.5km stage from Reims was raced at relatively sedate pace after the exertions of Monday's stage finale on the lumps and bumps of Champagne country, where Egan Bernal opened up a five-second gap on Ineos team-mate and British defending champion Geraint Thomas. "I was just looking in front, making sure I stayed upright", said Thomas, who had a scare on stage 1 when he flew over barriers but avoided injury.
A three-man breakaway featuring Frenchman Yoann Offredo, Swiss Michael Schaer and Belgian Frederik Backaert was kept on a tight leash by the peloton and they were all reined in 16 kilometres from the finish as Deceuninck-Quick Step worked to set up Viviani's victorious sprint.
The trio was eventually caught with 17 kilometers left, in the small Cote de Maron climb, leaving the spotlights on the fastest men of the peloton.