The Foxes were 5,000-1 shots to clinch the trophy at the start of the campaign, but they have defied the odds to become England's 24th different league winners.
Below are some of the best reaction to their success:
"Congratulations to both Leicester and my friend Claudio Ranieri for their historic win of the Premier League."
Incoming Bayern Munich head coach Carlo Ancelotti
Leicester city..🏆champion.— Mario Balotelli (@FinallyMario) May 2, 2016
Congratulations to the players and to an amazing manager as RANIERI! 👏🏾🙌🏾🙏🏾
"Congratulations to Leicester city on winning the premier league! What an incredible achievement!"
Fenerbahce striker Robin van Persie
"Congratulations to @LCFC what an amazing break from the norm. Yes they have individual brilliance but team ethic magnificent all season !!"
Former Manchester United and Stoke City defender Danny Higginbotham
"Congratulations to Leicester on winning the league title. What an unbelievable performance over the course of the season!"
Manchester United midfielder Bastian Schweinsteiger
Leicester City have won the Premier League. The biggest sporting shock of my lifetime, and it's only my team.— Gary Lineker (@GaryLineker) May 2, 2016
"Buzzin for all the lads back at Leicester right now some achievement that is #champions."
Leicester winger Tom Lawrence, who is on loan at Cardiff City
"Congrats to Leicester City what a feat. Spurs gave it everything and will represent the PL in the Champions League very well next season."
Ex-Spurs midfielder and manager Glenn Hoddle
"It's been on the cards for a while... just let that sink in for a sec,But ...WOW.. Leicester are champions... Absolutely superb. Well done."
Former Liverpool striker Robbie Fowler
CHAMPIONS!!!! pic.twitter.com/pFtvo5XUNx— Christian Fuchs (@FuchsOfficial) May 2, 2016