Nigel Pearson's side claimed a 2-1 win over Sheffield Wednesday on Friday, knowing that promotion to the top flight would be confirmed if results on Saturday went their way.
QPR fell to defeat at manager Harry Redknapp's old club Bournemouth, while Derby County could only draw with Middlesbrough, handing Leicester an unassailable lead at the top of the table.
That brings to an end the club's decade-long exile from England's top tier, with Leicester having suffered relegation from the Premier League in 2004.
It also soothes the heartache of last year's play-off semi-final loss to Watford, when Anthony Knockaert - who scored the winner against Wednesday - missed a last-gasp penalty at Vicarage Road before seeing Troy Deeney score at the other end to take the hosts to Wembley.
Pearson declared after the Hillsborough victory that his sights were set on winning the title and Burnley's 1-1 draw at Watford has left his side nine points clear at the top with six games to go.
He told BBC Sport after the game: "I want us to win every game that we can and I want us to be champions, but we'll have to fight very hard to do that."
Leicester have won the second-tier crown on six occasions in an illustrious history that includes 46 seasons at the highest level.
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