Bob Iger, chairman and CEO of The Walt Disney Company, made the announcement on Thursday.
Horn, 69, most recently served as president of Warner Brothers and co-founded Castle Rock Entertainment. He oversaw the hugely successful runs of the "Harry Potter" and "The Dark Knight" movies at Warner Bros. and is one of the highest-profile executives in Hollywood.
"Alan not only has an incredible wealth of knowledge and experience in the business, he has a true appreciation of movie making as both an art and a business," Iger said in a statement. "He's earned the respect of the industry for driving tremendous, sustained creative and financial success, and is also known and admired for his impeccable taste and integrity."
At Disney, he will oversee worldwide operations for live action and animated films, including those from Pixar and Marvel. He begins on June 11, just under two months after former chairman Rich Ross stepped down in a move widely seen as taking responsibility for blockbuster bomb "John Carter."
"I'm incredibly excited about joining The Walt Disney Company, one of the most iconic and beloved entertainment companies in the world," Horn said in a statement. "I love the motion picture business and look forward to making a contribution as part of Bob Iger's team working closely with the dedicated and talented group at the studio."
Disney is the parent company of ABC7.
The Associated Press contributed to this report.