Schmeichel joined Leicester from Leeds United in the summer of 2011 and has played a key role in the club's rise to become a major force in the Premier League.
Schmeichel made 478 appearances for Leicester City, helping the club win the Championship title in the 2013/2014 season as well as an unlikely Premier League triumph in the 2015/2016 season.
The 35-year-old also captained the Foxes to FA Cup success over Chelsea last year.
In a post on Twitter confirming his exit from the King Power Stadium, the former Manchester City goalkeeper wrote: "After 11 incredible seasons, I’ve made the difficult decision to leave Leicester."
"It’s been more than just a club to me, it’s been a place where I’ve made lifelong friends and memories - it has been my home.
"I wanted to share some of my favourite memories with you all."
Leicester chairman Aiyawatt Srivaddhanaprabha added: “Throughout his time with us and particularly as a captain and vice-captain, Kasper has always been a player willing to stand up and take responsibility, leading the team with distinction. His influence and his leadership on and off the pitch speak volumes about him as a professional, as a football player and as a human being.
“I know Leicester City supporters share the respect we all have for a player of Kasper’s standing after all his accomplishments as a footballer and captain and will join me in wishing him the very best for the next stage of his career in France with OGC Nice.
“It’s clear to everyone who has watched him perform that Kasper has given everything to Leicester City every time he has played and the experiences shared between him, the Club and our supporters over the last 11 years mean he will always remain a part of this family.”
Nice, who finished fifth in Ligue 1 last season, have also recently signed former Arsenal and Juventus midfielder Aaron Ramsey.
