Robert Downey was born in Manhattan, New York City, New York, the younger of two children. His father, Robert Downey, Sr., is an actor, writer, producer, cinematographer, and director of underground films, and his mother, Elsie (née Ford), is also an actress and appeared in Downey, Sr.’s films. His paternal grandfather was of Lithuanian Jewish ancestry and his paternal grandmother was of Irish Canadian and Hungarian ancestry. His mother is of Scottish, German, and Swiss German descent. His father was born “Robert Elias”, and changed his last name to “Downey” (after his stepfather James Downey), when he was a minor and wanted to enlist in the Army. He and his older sister, Allyson, grew up in Greenwich Village.
As a child, Downey was “surrounded by drugs”. His father, a drug addict, allowed Downey to use marijuana at aged six, an incident which his father has said he now regrets. Downey stated that drug use became an emotional bond between him and his father: “When my dad and I would do drugs together, it was like him trying to express his love for me in the only way he knew how.” Eventually, Downey began spending every night abusing alcohol and “making a thousand phone calls in pursuit of drugs”.
During his childhood Downey had minor roles in his father’s films. He made his acting debut at the age of five, playing a sick puppy in the absurdist comedy Pound (1970), and then at aged seven appeared in the surrealist Greaser’s Palace (1972). At the age of ten, he was living in England and studied classical ballet as part of a larger curriculum. He attended the Stagedoor Manor Performing Arts Training Center in upstate New York as a teenager. When his parents divorced in 1978, Downey moved to California with his father, but in 1982 he dropped out of Santa Monica High School and moved back to New York to pursue an acting career full-time.
Downey and Kiefer Sutherland, who shared the screen together in the 1988 film 1969, were roommates for three years when he first moved to Hollywood to pursue his career in acting.