The 21-year-old Yorkshireman started on the fourth row of the race but quickly got himself into the leading group and powered his way past the Swiss pair of Mathias Flueckiger and Nino Schurter to take control on the fourth of seven laps.
Flueckiger was the only man who could even remotely keep up as Pidcock kept the power down to win by 20 seconds, having time to snatch a Union Flag and hold it aloft as he crossed the line.
Pidcock adds the Olympic mountain bike title to his already long and diverse list of accolades, having won world titles in cyclo-cross, road and mountain bike events at under-23 level. This is Britain’s first Olympic mountain biking medal of any colour.
On a great day for Britain at the Olympics, Pidock’s triumph followed those of swimmer Adam Peaty in the men’s 100 metres breaststroke final and diving pair Tom Daley and Matty Lee in the synchronised 10 metres platform event.
Lauren Williams then booked her place in the women’s -67kg taekwondo final with pulsating win over Rio bronze medallist Ruth Gbagbi.
When asked how it felt to win gold, Pidcock told Eurosport: “Not real really. It’s pretty crazy that I became an Olympian and I was trying to tell myself at the start of the race it’s special just to be here.”
David Valero Serrano won the battle for bronze, 34 seconds down, the distance to the chasing pack underlining Pidcock’s dominance on the day.
Mathieu van der Poel, another of the pre-race favourites, pulled out after the fifth lap having crashed heavily early in the race.
Pidcock was racing in Japan less than two months after suffering a broken collarbone in a training crash on the road, but looked in supreme form as he bossed this race.
After Pidcock got himself in front his rivals gradually fell away, with Flueckiger the only one who could stay in touching distance.
But a slip for the 32-year-old on the fifth lap proved crucial as the man who tops the world rankings lost ground, then hope.
On his return from injury, Pidcock added: “Really hard. I haven’t done a good race since. I’ve trained really hard, I knew I was in great shape but there’s always doubt when I haven’t performed in a race.
“But once the race started, I knew I was in a good place. The heat, I mean, obviously I didn’t feel good but everyone just told me no-one will feel good.”