The 23-year-old has come on leaps and bounds since making a £20m move from Norwich City in the summer of 2018.
Maddison has become one of Leicester City’s best performers in his time at the King Power Stadium, leading to a first England cap last year.
Manchester United were rumoured to be interested in Maddison’s services but he has reaffirmed his commitment to Brendan Rodgers’ side until 2024.
"I'm so happy to sign a new contract for this football club," Maddison told LCFC.com.
"It's an incredibly exciting time to be a Leicester City player with so many positive things happening on and off the pitch and I'm delighted to be part of that. What we've achieved as a club this season is a huge step forward for us and I know there's so much more to come from this team.
"I've enjoyed every moment since joining Leicester City. The supporters have been incredible to me and we've a fantastic set of players in that dressing room who are determined to show what we're capable of doing together in both Europe and the Premier League next season."
Maddison will enjoy Europa League football next season after Leicester finished fifth in the Premier League last time out.
Maddison has scored 16 goals in 76 games for the Foxes.
Leicester City will begin their 2020/2021 season away at newly-promoted West Bromwich Albion on September 12.