Winks made 203 appearances for Spurs after coming through the club's youth ranks and was instrumental in their run to the Champions League final in 2019.
The 27-year-old spent last season on loan at Italian Serie A side Sampdoria, where he made 20 appearances in the top flight.
Winks could not prevent Sampdoria from getting relegated but his immediate task will be trying to get Leicester back into the Premier League following their own relegation last season.
Winks is new Leicester manager Enzo Maresca's first summer signing.
Speaking to LCFC TV, he said: “I’m delighted. I’m really excited for the challenge ahead. It’s an amazing club with great history and the facilities are incredible. I’m just so happy to be here and ready to get going.
“I’m looking forward to getting started, to have a full pre-season with the team and come here early to get ready for the games coming up. It’s going to be an important few weeks to get everyone ready and to push myself getting fit.
“I’m also looking forward to a new challenge and to challenge myself. Coming to a club like Leicester is the perfect chance to do that.”
Winks has won 10 caps for the England national team.
