Tim Merlier (Alpecin-Fenix) won on the cobbles of Le Samyn after a well-timed sprint to the finish.
With Dutch champion Mathieu van der Poel helping his team-mate with the leadout, despite riding with a broken handlebar, Merlier came to the front with around 150m remaining and celebrated as he crossed the line.
He pipped Rasmus Tiller (Uno-X) and Andrea Pasqualon (Intermarche-Wanty-Gobert) to victory.
Opinion: Van Aert, Pogacar and a golden age of superstars in Tokyo
The 205km course in Belgium saw several attacks throughout and a typically lively display from Van der Poel.
'That was a risky move' - Tim Merlier wins Le Samyn but takes a gamble with early celebration
A group of four riders - Kenny De Ketele (Sport Vlaanderen Baloise), Joey Rosskopf (Rally), Jan-Willem van Schip (Beat Cycling) and Enzo Leijnse (DSM) – led by 40 seconds when the race hit the cobbles at the halfway stage.
That advantage was whittled down with Mark Cavendish (Deceuninck-QuickStep) among those forming a smaller bunch at the front of the peloton.
Van der Poel also made a move to get across to the front group before Victor Campenaerts (Qhubeka ASSOS) attacked off the front with 30km remaining.
He was joined by Ludovic Robeet (Bingoal), but the duo couldn’t last the distance as Robeet was reeled in and then Campenaerts was caught with around 14km remaining.
Tim Merlier hails his team-mates after victory at Le Samyn
With the peloton together for the final stages, Van der Poel, riding with a broken handlebar, looked to lead out team-mate Merlier down the home straight.
Campenaerts and Tiller both attacked from distance but Merlier came through and celebrated as he crossed the line.
Tour de France
Blazin’ Saddles: Where to go now after opening week Tour de France fireworks?
Tour de France
Van der Poel pulls out of Tour de France to focus on Olympics