Dancing crowds dressed in the team's blue jerseys hugged each other and chanted songs honouring heroes such as manager Claudio Ranieri and striker Jamie Vardy, linchpins of Leicester City's first title triumph in its 132-year history.
"There is only one Ranieri," chanted fans in celebration of the Italian boss.
"This year I got married and had a baby, but this tops it all," said Steve Robinson, 26.
"It's going to be a big and long party, because we have waited a long time for this," added tourist guide Steve Bruce.
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Fans circled the city centre blaring their car horns, while others warned that European giants such as Barcelona were next in their sights as Leicester prepare to enter the Champions League for the first time.
"We're coming for you, (Lionel) Messi!" shouted Chris Whiting, 20, in a reference to Barcelona's star Argentine forward.
At Hogarths pub nearby, fans had cheered on Chelsea to prevent second-placed Tottenham Hotspur getting the win they needed to prolong the title race until Saturday, at least.
"I'm going to party! I've been supporting Leicester since I was 14 years old, can you imagine what this means for me?" said Caroline Wilkins, 60, who added she watched the match with a friend because her husband hates football.
"I feel on top of the world, I feel I'm in heaven!"
Whiting said he had started to fear the title might slip through Leicester's fingers when Tottenham were two goals up in the first half of the game.
"I still can't believe it... I started worrying about the next game," Whiting said.