Kai Havertz scored the only goal of the game as the Blues put on a tactical masterclass in Porto.
With only three shots on target, this was not a game filled with many clear-cut opportunities. However, the continuous tactical battle certainly made for thrilling viewing.
Speaking after the win, Tuchel told BT Sport: "To share it with everybody is incredible. We made it. Wow. I don't know what to feel.
"I was so grateful to arrive a second time [in the final]. I felt different. We were somehow... You could feel it getting closer.
"The [players] were determined to win this. We wanted to be a stone in their shoe. We encouraged everybody to step up and step out, to be more brave and create dangerous counter-attacks.
"It was a tough physical game. We had to help each other out."
Story of the match
Pep Guardiola fielded a surprise pivotless midfield in a bid to catch out Tuchel and the Blues, but the move backfired and City paid the toughest price.
When Chelsea paid Bayer Leverkusen £70million for Havertz last summer eyebrows were raised in some quarters, but Chelsea were convinced of the 21-year-old's pure talent.
And now the classy forward has ended a testing campaign that included a battle with Covid-19 with a goal of the utmost quality - on the highest stage and at the perfect time.
In just 124 days Tuchel has transformed Frank Lampard's muddled men into mean tactical machines - and champions of Europe.
Guardiola has spent five years honing City for European dominance, but that frustrating wait goes on.
Guardiola will keep grinding, but Tuchel has quickly built up something of an Indian sign over City's Catalan coach.
Chelsea's third win over City in six weeks clearly ranks most highly, but also cements Tuchel's arrival as a genuine tactical master.
The 47-year-old arrived from Paris Saint-Germain in January with a fiery reputation, but has reinvented himself as a taskmaster with a joyful spirit and a tendency to tease the best from his players.
Tuchel insisted he did not fear the brevity of his 18-month contract on his arrival at Chelsea, admitting even a five-year deal would not save his skin should he underperform.
Such candid talk - always delivered with a reassuring smile - has proved a breath of fresh air for Chelsea's entire set-up, from boardroom to boot room.
Just as in Munich nine years ago, so now Chelsea had to battle for Champions League glory the hard way.
For that breakthrough triumph in 2012, Andre Villas-Boas had to fall on his sword before Roberto Di Matteo could oversee a stunning penalties victory over Bayern Munich.
Jump forward all but a decade, and again the Blues are champions of Europe - in another season where two men have taken the Stamford Bridge helm.
Former boss Lampard will sit back somewhere with a wry smile at tonight's events, doubtless delighted for his club - but also surely with regrets not to be in the dugout.
The 41-year-old was a central character in that 2012 victory, and had started this season as a Chelsea boss desperate to build a lasting managerial legacy.
Lampard failed to blend the £220million-worth of summer transfer talent though, and paid with his job in January.
And so in came Tuchel, the demanding and discerning former Paris Saint-Germain boss, on a clear brief to generate immediate results.
The spectacular transformation has owed as much to sharp tactical acumen as shrewd people management.
Tactical masterclass from Tuchel
Any fears of a tight affair were immediately dispelled at the top of the night.
Timo Werner missed his first of two sitters when Havertz cut back to him in the area, while Ben Chilwell had to conjure a full-stretch clearance at the other end.
Werner's second miss was almost a bigger let-off for City than the first, as the Germany striker overran Havertz's inside ball, muddled up his feet and scuffed a low-power effort for an easy Ederson save.
Just when the half looked to peter out goalless though, Mount spun on the ball on the left wing and delivered the killer long-range through-ball for Havertz.
Werner raced out to the left to create the space, Havertz ghosted through and nicked the ball around the fast-advancing Ederson - before tapping into the empty net.
Chelsea had lost influential centre-back Thiago Silva to a groin injury just past the half-hour, but Andreas Christensen settled quickly. And the Blues were good value for their 1-0 half-time lead.
The Belgium star's night went from bad to much, much worse moments later, when colliding with Rudiger. After lengthy treatment the ex-Chelsea playmaker trudged off in tears, with a possible broken cheekbone.
Guardiola eventually gave up the ghost on his pivot-free midfield just past the hour, with Fernandinho replacing Bernardo Silva.
Christian Pulisic had a golden chance to cement Chelsea's advantage when played in by Havertz, only to scythe his dinked effort well wide.
Guardiola's men refused to give up though, cajoling again and again, and moving the ball in their neat patterns.
An age-long seven minutes of added time left Chelsea players and fans biting nails alike, and Mahrez so nearly equalised with a snap shot at the very, very last.
But the ball sailed just wide, and Chelsea were champions of Europe again.