The 24-year-old Algeria international midfielder has made over 50 appearances for the Foxes since signing from French side Le Havre in January 2014.
City announced the contract extension after Mahrez impressed last term as they stayed in the Premier League.
"Leicester City are delighted to announce that we have agreed terms with Algerian international Riyad Mahrez on a contract extension to June 2019," Leicester said on their official website.
Mahrez is poised to make his 50th league appearance for the Foxes in Saturday's Premier League season opener with Sunderland at the King Power Stadium.
Source : PA
Source: PA