An American actor. The son of director Stephen Gyllenhaal and screenwriter Naomi Foner, Gyllenhaal began acting at the age of ten. Following his first lead role in 1999's October Sky, he starred in the indie cult hit Donnie Darko (2001), in which he played a psychologically troubled teenager alongside his older sister, actress Maggie Gyllenhaal. In 2002, he starred in another indie film, The Good Girl, alongside actress Jennifer Aniston. In 2004, he appeared in the science-fiction film The Day After Tomorrow, portraying a student caught in a cataclysmic global cooling event.

Gyllenhaal then played against type as a frustrated Marine in Jarhead (2005). The same year, his role as Jack Twist in Brokeback Mountain earned him critical acclaim and an Academy Award nomination for Best Supporting Actor. He has since played the lead roles in many notable films, including Zodiac (2007), Prince of Persia: The Sands of Time (2010), Love and Other Drugs (2010), Source Code (2011), and End of Watch (2012).

Gyllenhaal was born in Los Angeles, the son of film director Stephen Gyllenhaal and film producer and screenwriter Naomi Foner. Maggie Gyllenhaal, his older sister and also an actress, appeared with Jake in the movie Donnie Darko. Gyllenhaal's father, who was raised as a Swedenborgian, is of Swedish and English descent, and is a descendant of the Swedish noble Gyllenhaal family. Jake's last native Swedish ancestor was his great-great-grandfather, Anders Leonard Gyllenhaal. Jake Gyllenhaal's mother is from a Jewish family from New York City, and Gyllenhaal has said that he considers himself "more Jewish than anything else." On his 13th birthday, Gyllenhaal performed a "barmitzvah-like act, without the typical trappings", volunteering at a homeless shelter, because his parents wanted to instil in him a sense of gratitude for his privileged lifestyle. His parents insisted that he have summer jobs to support himself, and he thus worked as a lifeguard and as a busboy at a restaurant operated by a family friend.