Downey, Jr. was born in New York City, New York. He is the son of Elsie and director Robert Downey Sr. Downey Jr.'s father was born with the surname Elias, and is half Irish and half Jewish while Downey Jr.'s mother is half Scottish and half German.

His first film role was playing a puppy in his father's film POUND (1970).

Having appeared in several small film roles from an early age, at 20 he joined the cast of Saturday Night Live, but only appeared there for one season. He went on to star in The Pick-up Artist in 1987. The same year, he portrayed the drug-addicted rich boy in Less Than Zero, a role that proved prophetic. In 1992 Downey starred as Charlie Chaplin in Chaplin, a role which garnered him an Academy Award nomination for Best Actor. His other films include Only You, Natural Born Killers, and Restoration, a film adaptation of Rose Tremain's novel of the same name.

In 2000, he became an acclaimed regular on the television series Ally McBeal. He won a Golden Globe award for his work on the show and was also nominated for an Emmy. He also appeared as a writer and singer on Vonda Shephard's Ally McBeal: For Once in My Life album and sang in a duet with Sting on The Police's "Every Breath You Take" hit dating from 1983.

Downey, Jr. appeared in Elton John video "I Want Love" in 2001. On November 23, 2004, he released his debut musical album "The Futurist" on Sony Classical, for which he designed the cover art. He was invited to open for Duran Duran in 2005. He had to decline the offer due to film commitments.

He works on a regular basis again, with three movies released in 2005 and seven announced for 2006. Among them are the already-released Kiss Kiss, Bang Bang, Good Night, and Good Luck. and The Shaggy Dog, as well as the upcoming A Scanner Darkly, Zodiac, and Fur.

Downey, Jr. dated actress Sarah Jessica Parker in the 1980s, and was married to actress Deborah Falconer on May 29, 1992, a marriage that ended in divorce on April 26, 2004. They have a son named Indio. He married producer Susan Levin, (who he met on the set of Gothika) in a Jewish ceremony at Amagansett, New York, on August 27, 2005.

Downey, Jr. practices Wing Chun Kung Fu. Downey Jr. is good friends with journalist and actor, Sam Slovick.

On June 23, 1996, Robert Downey, Jr. was arrested for driving drunk and being in possession of Mexican Black Tar heroin, crack, cocaine and an unloaded .357 Magnum revolver.

On November 6, Malibu Municipal Judge Lawrence Mira sentenced Downey to three years probation for weapons and drugs charges. However, just over one year later on December 8, 1997, Judge Mira sentenced Downey to six months in jail for violating parole. Eighteen months later, Downey returned to Corcoran State Prison to serve a three-year sentence for a parole violation again on July 16, 1999.

A California state appellate court ordered Downey released from his term in state prison due to a sentencing error made by his trial judge in August 1999. An appeals court panel ordered his immediate release. The appeals court said Superior Court Judge Lawrence Mira did not take into account time Downey had spent in court-ordered rehab and ruled that the actor ended up serving more than enough time to fulfill his sentence.

Downey was arrested again in a Palm Springs, California hotel for cocaine and Valium possession and being under the influence of a controlled substance on November 25, 2000.

On April 24, 2001, he was arrested in Los Angeles for being under the influence of a controlled substance after he was found wandering in an alley. He was not charged.

The charges from the November 2000 arrest were dismissed in July 2002 due to California's Prop. 36. The judge had determined that Downey had been drug free for 14 months.

Downey has not had any more public incidents since that time and has allegedly remained clean and sober soon after he said that his father is the one who introduced him to drugs by offering him a marijuana joint at age 8. Downey also has revealed hesuffers from bipolar disorder, also known as manic depression.