"Brett has a sincere love of movies and film history, and we are excited to welcome him to our group of supporters," Bill Kramer, the museum's managing director of development, said in a statement Wednesday.
The academy established the museum's capital campaign in 2012 and has already secured more than half of the campaign's $300 million goal in commitments.
"Thanks to the generosity of founding supporters like Brett, we are now able to realize the long-held dream of the academy and that of the global film community to build a museum dedicated to the history and future of the movies," said Iger.
"I feel blessed to be part of such a magnificent museum. I was blown away by the recent Kubrick exhibit at LACMA, which the academy co-sponsored. I couldn't be more excited that our academy will finally have its own museum that will preserve and exhibit cinema's greatest work," said Ratner.
The Academy Museum will be located next to the Los Angeles County Museum of Art in the historic Wilshire May Co. building. It is slated to open in early 2017.
Ratner's films include the "Rush Hour" trilogy, "The Family Man," "Red Dragon," "X-Men: The Last Stand," "After the Sunset" and "Tower Heist."