The Quick-Step Floors sprinter streaked to his second victory in a row in the German one-day race, beating 2012 winner Arnaud Démare (Groupama-FDJ) into second place, just as he did last year, with 2014 winner Alexander Kristoff (UAE Team Emirates) finishing third.
"I was second in the Cadel Evans Race, Gent-Wevelgem and RideLondon, so to finally win a World Tour one-day race this year feels incredible," Viviani said on the Quick-Step website, having notched up the team's 55th victory of 2018.
"It's also my first victory in the beautiful maglia tricolore, which is something special that I will remember for the rest of my life."
Viviani's second win in Hamburg equals the record held by American sprinter Tyler Farrar, who won the event in 2009 and 2010.
"The team again did a perfect and impressive job: Iljo Keisse pulled the entire day, in his first race since June, then we had Rémi Cavagna and Kasper Asgreen for the hilly part of the race, where they kept things together, before Davide Martinelli, Michael Mørkøv and 'Saba' [Fabio Sabatini] took over," Viviani explained.
"We studied the closing part of the race yesterday evening and knew we had to be in the front for the last three kilometres, which were really technical. It's a pleasure to be part of this team, the best in the world, and I feel really luck to be a member of 'The Wolfpack'."
Viviani was on Démare's wheel with 400 metres left to race, who in turn was led out by his teammate Jacopo Guarnieri. The Italian champion left it until 150 metres left to go before emerging from the Frenchman's slipstream to take the win.
Démare was disappointed to finish second to Viviani for the second year in a row in Hamburg, but thanked his Groupama-FDJ teammates for their efforts.
"Last year I was happy to get second, but this year I'm disappointed, as I'd been put into the perfect position thanks to the amazing work done by Ramon Sinkeldam and Jacopo Guarnieri," Démare said.
Kristoff's third place was the fourth time the Norwegian had been on the podium at the Cyclassics Hamburg, having finished third in 2013, before winning the race the following year, and then finishing second in 2015.
"My teammates Roberto Ferrari and Marco Marcato helped me get to the front, and I was able to launch myself well into the sprint. I didn't have the legs to win, however, but I was good enough to get third, and I'm satisfied with that," he said.
If you've ever wanted to know what it feels like to be part of a top-level cycling team, and to be on the ground, inside the barriers, at the Tour de France, then RUNNING WITH WOLVES will take you there. It is available to rent for $3.99 USD or buy for $6.99 USD.