The bearded star, who portrays real-life adventurer Scott Fischer in the film, was photographed completely naked during one take, with just a small piece of black material taped to his crotch to cover his manhood.
The movie is based on author Jon Krakauer's book Into Thin Air, which documents the tragic 1996 Mount Everest disaster that claimed the lives of eight climbers, including Fischer, and left several others stranded.
Krakauer himself was a survivor of the tragedy.
Zero Dark Thirty star Jason Clarke will play Hall, while Josh Brolin is also part of the cast.
Gyllenhaal is no stranger to stripping off on camera - he previously disrobed for Brokeback Mountain and Love and Other Drugs.