About 100,000 Manchester City fans lined the streets for a victory parade for the Premier League champions.
City clinched the title - their first since 1968 - with a dramatic 3-2 win over Queens Park Rangers on Sunday.
The players' arrival at Manchester Town Hall, where the parade started, was met by rapturous applause from City fans.
However, the club issued an apology to rivals Manchester United after striker Carlos Tevez was seen carrying a banner with the message "RIP Fergie".
Tevez also apologised for the message, directed at United manager Sir Alex Ferguson, saying he "didn't mean any disrespect".
The squad followed the Albert Square gathering with a 1.8-mile open-top bus parade through the city centre.
Before boarding the bus, the players thanked the supporters before the team held the Premier League trophy aloft to the crowd, accompanied by Queen's We are the Champions.
Captain Vincent Kompany told the fans in Albert Square: "We want to say thank you to you guys. Thank you, thank you, thank you."
England winger Adam Johnson said: "Everything we did was for the fans. It's good we can repay them with trophies."
City manager Mancini, wearing his trademark blue and white City scarf, described the final minutes of the decisive match with Queens Park Rangers as "the best and worst five minutes" of his and his players' lives.
He then told the supporters: "I think we should be proud of these players because they did everything for you [the fans] - they wanted to win this championship for you."
The bus meandered slowly from Albert Square through Princess Street, Portland Street, Deansgate, then St Mary's Gate before finishing in Corporation Street at 20:04 BST - almost 20 minutes behind schedule - to constant cheers and the chorus of Championes.
Fans, many with their faces painted in the club's colours, awaited the arrival of the players in Albert Square by watching highlights of the nail-biting win over QPR - and celebrating the goals with as much jubilation as when they were scored.
Craig Smith, 21, of Colwyn Bay in north Wales, said it was an "amazing feeling" to be part of the celebrations.
He said: "I've come to Manchester to see the champions of England.
"It would have been a massive day anyway but after the drama it's even better."
Andrew Hyland was with his daughter Isabelle, eight, to cheer on the newly crowned champions. Mr Hyland admitted shedding tears during Sunday's match.
"It was unbelievable, typical City.
"My emotions were all over the place there were tears of desperation then so much relief when the final goal went in."
Greater Manchester Police estimated 100,000 fans had attended the parade, with 12,000 in Albert Square alone. There was just one arrest.
Assistant Chief Constable Terry Sweeney praised the supporters.
He said: "There was a friendly, carnival atmosphere throughout the parade which passed off without incident and was a great showcase for Manchester."
Sir Richard Leese, leader of Manchester City Council, said: "City fans have waited a long time for this - as can be seen from the thousands of people on the streets celebrating their victory, and suddenly the last 40 years of chasing the championship doesn't seem to matter.
"The fans have done us proud tonight as Manchester takes centre stage across the world once again."
City had led the league for much of the season but were overtaken by United, who were eight points clear with six games to go. But the Old Trafford side dropped points in their last few games and City went into the final day knowing a win would make them champions.
But QPR led 2-1 after 90 minutes and Manchester City needed two injury-time goals to win the game and clinch the title.
Over the years City have been mocked by United fans, who, until City's FA Cup win last year, had documented their wait for a trophy with a banner at Old Trafford's Stretford End.
When Manchester United were eight points clear in early April, leading High Street bookmaker Betfred, founded by United fan Fred Done, paid out more than £500,000 to punters who had backed the Red Devils.
Mr Done said on Twitter the lead "was just too much for City" and "I've not got it wrong this time".
Meanwhile, United players drowned their sorrows two miles away at the club's annual player of the year awards night at Old Trafford.