Mathieu Van Der Poel became the first Dutch winner of Milano Sanremo for 38 years after a masterful attack atop the Poggio ascent.
The Alpecin-Deceuninck rider crossed the finish line alone on Saturday to claim the third Monument victory in his career.
Filippo Ganna finished second for Ineos Grenadiers, out-sprinting Wout Van Aert and Tadej Pogacar in group two.
The 28-year-old will look to carry his winning form into the Ronde Van Vlaanderen and Paris-Roubaix in April.
Van Der Poel said: "This is one of the races I really wanted to win, and the way I won it today is beyond expectation".
(This was Van Der Poel's first road-race victory of the season - Photo: Clemence LN, Wikimedia Commons, Creative Commons Attribution-Share Alike 4.0)
The early breakaway formed within the opening fifteen kilometres, with nine riders bold enough to spend the day up front in the longest race on the World Tour calendar.
Mirco Maestri and Alessandro Tonelli were joined by team-mates Samuele Rivi and Samuele Zoccarato; Alexandre Balmer and Jan Maas represented Jayco AlUla, with Alexandr Riabushenko, Aloïs Charrin and Negasi Haylu Abreha completing the front group.
The teams of the favourites controlled the gap to the breakaway, keeping it below four minutes throughout the race.
Julian Alaphilippe and Tadej Pogacar were involved in early crashes but returned to the peloton without much stress.
Movistar's Alex Aranburu suffered a more untimely incident, crashing with just over 45 kilometres to go, though he'd also make it back to the main group before the Cipressa.
Approaching the Cipressa, tensions were high and crashes continued; Sam Bennett had to abandon as he tangled with an unsignalled bike rack.
The race to the Cipressa saw Michal Kwiatkowski of Ineos and Jan Tratnik of Team Jumbo-Visma tangle, ending their hopes of impacting the classic.
Lotto Dstny and Ineos Grenadiers completed the catch of the early breakaway at the foot of the Cipressa climb.
UAE Team Emirates sent Diego Ulissi and Felix Großschartner to the front of the peloton to weaken the sprinters.
Arnaud De Lie could not hold UAE's tempo, the young Belgian sprinter being distanced by the pace.
Bora Hansgrohe rider Nils Politt tried an opportunistic attack between the Cipressa and Poggio but was caught before the final climb.
Fred Wright led his Bahrain-Victorious team to the foot of the Poggio, the final chance for the climbers to apply pressure.
Tim Wellens and Tadej Pogacar accelerated off of Bahrain's frantic pace, the Belgian reducing the lead group to eight riders.
With one kilometre to the top of the climb, Pogacar launched his attack, distancing the rest of the group.
Filippo Ganna, Wout Van Aert and Mathieu Van Der Poel bridged the gap to the Slovenian, and left Søren Kragh Andersen, Matej Mohoric and Jasper Stuyven behind.
Van Der Poel sat on the back of the quartet, counter-attacking over the top of the Poggio.
The gap opened to Pogacar, with Ganna sitting on his wheel and Van Aert starting to struggle.
The dutchman extended the distance between himself and the chasing trio on the Poggio descent.
By the closing kilometre, the gap hovered at around ten seconds, which the classics specialist held to win the opening monument of the season.
(Van Der Poel gave Alpecin Deceuninck their third World-Tour victory in ten days - Photo: Leif Jørgensen, Wikimedia Commons, Creative Commons Attribution-Share Alike 4.0)
Van Der Poel said: "I was really focused on this race since I started training again after the World Championships... I knew I needed some race days to get to my best level, and today I think this was my best level."