The in-form striker has been rewarded after scoring seven goals in his last four games in all competitions, a run of form that saw him win the Premier League Player of the Month award for March.
He has nine goals in his last nine games – having failed to score in his previous 12 matches – and netted his first Premier League hat-trick in the 5-0 win over Sheffield United on March 14.
After signing his new deal, Iheanacho told Leicester’s website: “I can’t express how I’m feeling. I’m excited, I’m happy, I’m overwhelmed! It’s a great moment and I’m happy that Leicester City gave me a new contract.
“It’s been a great time here. It’s not been easy, but there’s a lot of people here that are good people, great people to work with. They are nice people and they make me feel comfortable and welcome since I came in.
“It’s been really great being here. It’s like a family. I’m happy being here and hopefully I can stay here many more years.”
Iheanacho joined Leicester from Manchester City in 2017 and has gone on to score 32 goals in 117 games for the Foxes.
Incidentally, his new deal comes on the same day that he is set to play against his former club, with Leicester hosting Manchester City on Saturday, live on Sky Sports.