Denmark's captain, who recently played in the European Championship, joins Celtic as a free agent after spending last season with Anderlecht in Belgium.
Schmeichel previously played for Ligue 1 side Nice in the 2022-23 season after a long spell at Leicester City, where he won the Premier League in 2016 and the 2021 FA Cup.
Following 479 games for the Foxes during 11 seasons, he sits third in Leicester's all-time appearance list.
Schmeichel made his international debut in 2013 and has earned 105 caps for Denmark.
"I am absolutely delighted to join Celtic and can’t wait to get started," Schmeichel said.
"Celtic is one of the world's proper football clubs, a massive name and a place of real passion and success. Celtic is what football is all about."
The Dane will be reunited with Brendan Rodgers, who managed Leicester from 2019 to 2023 before returning to Celtic.
"I am really pleased to bring Kasper to Celtic," Rodgers said. "He is a real quality keeper and someone with the ability and personality to be great for us."
Schmeichel will join up with Celtic in the United States on a pre-season tour before they host Kilmarnock in their Scottish Premiership opener on August 4th.
