Groenewegen, 24, held off Andre Greipel (Lotto-Soudal) on the line to celebrate his first Tour stage win, making up for his fifth, two sixth places, a third, and second place in the previous sprint finishes.
"This is amazing. I was fighting with Kristoff for the right wheel. Before that, Robert, Paul and Tom kept me out of the wind," Groenewegen explained of the finale. "Primoz did a great job by pulling on the front of the bunch. I came out of the turn in second place. The sprint felt like it lasted a century and I just grab it.
"When I was young, I was looking at the Champs-Elysées stage on TV. Now I'm the winner here, it's wonderful."
Groenewegen made his Tour debut last year, with fourth place into Limoges the best result of his race. He finished the Tour with 164th place on the Champs-Élysées, when he was unable to sprint. He is now one from one when it comes to contesting the final stage of the race.
"This is a beautiful day for a win like this. We had loads of critics, but on the most important day for sprinters, we prove we can do it. We won on the Champs-Élysées, that is unbelievable," added the Dutchman, who had just four teammates for company on stage 21.
Groenewegen joins Jean-Paul van Poppel in 1988, Gerrie Knetemann in 1978, and Gerben Karstens in 1976 to have a stage of the Tour on the Champs-Élysées. The win breaks a four streak of German wins on the Champs-Élysées after two for Marcel Kittel and then two for Greipel.
The stage win also ensured that LottoNL-Jumbo finishes the Tour on a high following on from Primoz Roglic's success into Serre Chevalier. The team lost its GC rider George Bennett to illness and stage hunter Robert Gesink to a broken vertebra.
"We wanted to win with Primoz in the time trials, but it did not work out because of a crash in Düsseldorf, caused by the bad weather, and bad luck in Marseille yesterday," sports director Nico Verhoeven said, "Robert Gesink's crash and abandon after a week was a huge disappointment. George Bennett was in the top-10 for a few days, but then slowly dropped out. It turned out he was unwell and had to abandon the Tour, as well.
"Primoz's and Dylan's wins gave us the big highs we wanted. With all these experiences, we can make the next step."