Casillas has not featured in any game since suffering a heart problem in May 2019 during a training session with Porto.
Announcing his retirement in an emotional statement he posted on Twitter, the 2010 World Cup-winning captain said: “The important thing is the path you travel and the people who accompany you, not the destination to which it takes you.
“Because that with work and effort, I think I can say, without hesitation, that is has been the path and the dream destination.”
Los Blancos were quick to pay tribute to their former skipper, who appeared in 725 games for the club between 1999-2005.
During that period, he helped the Spanish side win five LaLiga titles, three Champions League trophies, two Copa del Rey’s and the Club World Cup on three occasions.
Commenting on his retirement, the club said: “Real Madrid CF wants to show his appreciation, admiration and love for one of the greatest legends of our club and world football.
‘The best goalkeeper in the history of Real Madrid and Spanish football came to our house when he was nine years old.
“Today, one of the most important footballers in our 118-year history, a player whom we love and admire, a goalkeeper who has enlarged the legend of Real Madrid with his work and with exemplary behaviour both inside and outside, says goodbye as a professional player.
“Iker Casillas belongs to the heart of Real Madrid and will be so forever. Real Madrid wants to convey to him and his family the affection of our club, which is the club of his life.”
Casillas’ former Real and Spain team-mate Sergio Ramos was quick to message the legendary shot-stopper, as he tweeted: “Soccer thanks you, friend. Forever a legend.”
Porto meanwhile posted a compilation video of Casillas’ highlights during his five-year spell with the Portuguese outfit, captioning the clip: “Thank you @IkerCasillas: Forever one of us.”
— FC Porto – Dobradinha 19/20 🏆🏆 (@FCPorto) August 4, 2020