This year's Tour is focused on history with its double celebration of Eddy Merckx and the first yellow jersey. Alaphilippe's magnificent attack in Epernay will surely echo down the ages in a similar fashion.
The Frenchman launched his raid from the peloton with 15km to go, quickly sweeping up Tim Wellens on the crest of the Cote de Mutigny after the Lotto Soudal rider tried his own luck earlier on the first of the stage's four categorised climbs to claim the polka dot jersey.
Ahead of the brutal finish, Alaphilippe deployed all of his panache as the consequences of a relatively long range attack began depleting his reserves.
The Frenchman powered up the climb and punched the air with a ferocious energy as he crossed the line, also claiming the yellow jersey as he holds a 20-second buffer over Wout van Aert (Jumbo-Visma).
"I’m speechless," an emotional Alaphilippe said. "I don’t realise what’s happening to me.
"I knew this stage suited me. I felt good so I accelerated in the Mutigny climb but I didn’t think I’d go alone.
"I gave everything. I heard I was 30 or 40 seconds ahead. It’s difficult to meet the expectations being the favourite. I made it. I’m delighted."
A who's who of puncheurs finished 26 seconds in Alaphillipe's wake, Michael Matthews (Sunweb) out-kicking Jasper Stuyven (Trek-Segafredo), Greg van Avermaet (CCC) and Peter Sagan (BORA-hansgrohe) at the line for second, the Australian unaffected by his earlier effort to chase back to the peloton after a crash.
"At the finish it was just everything I had left, and lucky it was good enough for second," Matthews said, who now sits 17 points behind Peter Sagan (76) in the green jersey competition.
"I really struggled today. I (rode with) pure heart...thinking about my baby, thinking about my wife."
Early in the stage, Wellens pulled clear from the bunch with Yoann Offredo (Wanty-Gobert), Stéphane Rossetto (Cofidis), Tim Wellens (Lotto Soudal), Paul Ourselin (Total Direct Energie) and Anthony Delaplace (Arkéa- Samsic). The quintet soon established a decent lead over the peloton which never exceeded the five minute mark.
Wellens launched his solo attack with 48 kilometres to go, bravely leading the race for another 33 kilometres before Alaphilippe sashayed away.
Race leader Mike Teunissen (Jumbo-Visma) finished over four minutes down and relinquished the yellow jersey to Alaphillipe, with Thibaut Pinot (Groupama-FDJ) and Egan Bernal (Team Ineos) taking five seconds on their general classification rivals after a split in the peloton.