Ditko was found dead on June 29 in his midtown Manhattan apartment, New York Police Department spokesman George Tsourovakas told CNN.
Ditko was born November 2, 1927 in Johnstown, Pennsylvania, according to his biography on IMDB.
Marvel President Dan Buckley said in a statement "the Marvel family mourns the loss" of Ditko.
"Steve transformed the industry and the Marvel Universe, and his legacy will never be forgotten," Buckley said. "Our thoughts are with his family, loved ones, and fans during this sad time."
Jim Lee, publisher of DC Entertainment (home to Batman and Superman), said in a series of tweets that while Ditko was known for co-creating Spider-Man, he did work on the DC side as well.
DC Comics also released a statement on their official Twitter account saying "Steve Ditko was one of the most amazing creators in the history of comics, and showed us there is a hero in all of us."