O'Neill, previously City's most successful boss having led them to two League Cup victories, saluted Claudio Ranieri's outsiders for proving romanticism still exists in football.
"It is absolutely extraordinary," he told ITV News.
"The team has lost three games. That in itself is a fantastic achievement. But to go and win the Premier League in this day and age when money seems to count, it is absolutely fabulous.
"Romanticism is still alive in football and that is great news for everyone.
"Leicester City have shown the way, shown how it can be done and great credit to all of them. To the players, the manager who has been terrific, the back room staff who have assembled the team. It's been a team effort from start to finish."
City were 5,000-1 no-hopers at the start of the season but their remarkable triumph was sealed with two games to spare when Tottenham were held 2-2 by Chelsea on Monday night.
copa mundial black Alan Shearer, who won the Premier League title as a player with Blackburn in 1995, claimed the Leicester story is "the biggest and best ever".
"When you consider who they had to take on in Manchester City, Manchester United, Arsenal, Chelsea, Liverpool and Tottenham and the vast sums of money these clubs have spent on players and managers, it's just one hell of a story," said Shearer in his Coral blog.
superfly cr7 red "It's certainly the biggest and best story I have ever seen in all my time in sport."
Jose Mourinho, who led Chelsea to the title last season, sent his congratulations to Ranieri and his all-conquering team.
women hypervenom ii In a CAA Sports UK statement, he said: "I want to congratulate everyone connected to @LCFC; players, staff, owners and fans. I lost my title to Claudio Ranieri and it is with incredible emotion that I live this magic moment in his career."
Elastico Superfly green Many pundits believe Leicester's success is a one-off and fear they will lose some of their star players such as Riyad Mahrez, N'Golo Kante and Jamie Vardy,
But former Tottenham manager Harry Redknapp insists there could be more to come from the Foxes.
He told talkSPORT: "They've got very wealthy owners there, I'm sure they'll strengthen and they'll make sure that people there are looked after and they'll keep the players. It'll be interesting to see next year again."
ace 16+ green ozil Kasabian guitarist and Foxes fan Serge Pizzorno has no such worries and says he will not care if City are playing non-league football 10 years from now.
The Leicester band are celebrating City's triumph with a Bank Holiday double-header gig at the King Power Stadium at the end of May.
Pizzorno wrote in the Guardian: "Winning the Premier League? After that, even if we get relegated and we're in the Conference in 10 years, I won't care. We'll always have that.
"I first started thinking we could qualify for the Champions League when we were still top at Christmas, then carried on picking up points in January. I thought that if we kept everyone fit until the end of the season, I didn't see why we couldn't finish in the top four.
"As for next season: we all live in Leicester so all my pals are coming in and we're having a Champions League draw party - it's already on the calendar."
