Massed ranks of rowdy cycling fans, many of whom had camped overnight, packed the roadsides cheering the riders all the way up the magnificent beyond category Col du Galibier mountain.
Slovenian superstar Pogacar's triumph was built by his UAE Team on the ascent with three teammates still with their leader when all the 2020 and 2021 champion's rivals had been stripped of their shattered sherpas.
"I wanted to hit hard today. I've been training here for several weeks already and everything went according to the plan we set," said Pogacar, whose team bore the brunt of the famous Galibier headwind all day.
Two-time defending champion Jonas Vingegaard of Denmark finished fifth at 37sec after keeping pace on the way up, but losing time on the way down.
Belgian Quick Step rider Remco Evenepoel, just 24 years old and on his first Tour de France, finished 35 seconds off the pace in second place, retaining second overall at 45sec.
"It was a good stage for me and the team," said a smiling Evenepoel. "Neither myself nor Jonas were as fast as Tadej today. There will be others."
Pogacar, 25, reclaimed the overall lead he took on stage two in Bologna.
Evenepoel suggested he had been more prudent than the day's winner.
"On the way down I slipped a couple of times and thought about the risk. I did what I could," he said.
Carapaz crushed
Vingegaard's Visma team also appeared visibly weaker than during their dominant 2023 display when the Dane collected his second triumph on the Tour.
Overnight leader, Education First's Richard Carapaz, was the big loser on the day. The Ecuadorian gave up over five minutes.
Pogacar, winner in 2020 and 2021, is attempting to become the first rider since 1998 to win the Giro d'Italia and Tour in the same year.
The short 134km run from Pinerolo marked the end of an entertaining and picturesque race start in Italy.
The first four stages took in Florence, the Adriatic coast, Bologna and the Piedmont region on the French border beside Turin.
Pogacar's Team UAE hogged the front during the 25km final ascent, taking it in turns to set the pace as their rivals wilted.
Runner-up in the past two editions behind Vingegaard, Pogacar attacked less than 1km from the summit, and it was the last his rivals saw of him, so winding was the route.
On Wednesday, stage five will see Biniam Girmay, Jasper Philipsen, Mark Cavendish and the other fast men jostle for position as the 177km route snakes through valleys between Saint-Jean-de-Maurienne and the village of Saint-Vulbas.
The stage is notable for the fact times will be frozen at 3km from the line even if there is no fall under a new International Cycling Union safety initiative for flat stages.
