The 31-year-old former England international was a free agent after leaving Southampton at the end of the 2020/2021 season.
Bertrand spent seven years at the South Coast club, having initially joined on loan from Chelsea in the summer of 2014 before making the deal a permanent one.
Bertrand made 240 appearances for Southampton in his time at the club and will provide valuable experience for Brendan Rodgers’ side, who have finished fifth in the Premier League for the past two seasons.
After completing his move, Bertrand told Leicester City’s official website: 'I'm really happy to be here; joining Leicester really complemented my inner ambitions and what I still want to achieve in my career.
'Leicester have built something amazing over the years, especially since Brendan Rodgers has come in. It's fantastic to be a part of this fantastic club and I'm going to give my all to try and do the fans proud.'
Bertrand is Leicester City’s third summer signing following the acquisitions of Patson Daka from Red Bull Salzburg and Boubakary Soumare from French champions Lille.
Bertrand won the 2012 UEFA Champions League and the 2013 Europa League while at Chelsea.
Leicester begin their 2021/2022 season at home to Wolverhampton Wanderers on August 14.
