The showdown on 29 May was originally scheduled for the Ataturk Stadium in Istanbul.
But as soon as Chelsea beat Real Madrid on 5 May to advance to the final, pressure started for a switch to an English venue.
That campaign grew after the British government placed Turkey on its red list of countries meaning fans would have to quarantine on their return home.
Discussions
However, following talks between officials from Uefa, their counterparts at the English Football Association and the British government, Wembley has been ruled out but Porto has been lined up instead.
With Portugal on the green list - no quarantine necessary - City and Chelsea will get 6,000 tickets each for the match at the Estádio do Dragão.
"To deprive supporters of the chance to see the match in person was not an option and I am delighted that this compromise has been found," said Uefa president Aleksander Ceferin.
"Fans have had to suffer more than 12 months without the ability to see their teams live and reaching a Champions League final is the pinnacle of club football," added Ceferin.
It is understood the British government refused to agree to Uefa’s request to waive quarantine exemptions for tournament sponsors, foreign media and Uefa officials.
Changes
Last year's final was held in the Portuguese capital after Uefa reconfigured the tournament due to the first wave of the coronavirus pandemic.
All the knockout matches were one-off games instead of the usual two legs. Bayern Munich lifted the trophy after beating Paris Saint Germain 1-0.
This year, City eliminated the French outfit 4-1 on aggregate to reach the final for the first time.
It will be Chelsea’s third appearance in the final. They lost on penalties in 2008 to Manchester United and beat Bayern Munich by the same process four years later at the Allianz Arena in Munich.
Didier Drogba, who equalised in the dying seconds of normal time, slotted home the winning penalty for the west Londoners.
