Robert John Downey Jr. (born April 4, 1965), also known as RDJ, is an American actor. His films as a leading actor have grossed over $14 billion worldwide, making him one of the highest-grossing actors of all time. In 2008, Downey was named by Time magazine as one of the 100 most influential people in the world. From 2013 to 2015, Forbes listed him as Hollywood's highest-paid actor. His accolades include a Golden Globe Award, BAFTA Award, Academy Award, and two Primetime Emmy Award nominations.

At age five, Downey made his acting debut in his father Robert Downey Sr.'s 1970 film Pound. He subsequently worked with the Brat Pack in Weird Science (1985) and Less than Zero (1987) teen films. Downey's portrayal of Charlie Chaplin in the 1992 biopic Chaplin garnered him a BAFTA Award for Best Actor and his first Academy Award nomination. Following a stint at the Corcoran Substance Abuse Treatment Facility on drug charges, he joined the TV series Ally McBeal in 2000 and won a Golden Globe Award for the role. Downey was fired from the show in 2001 in the wake of additional drug charges. He stayed in a court-ordered drug treatment program and has maintained his sobriety since 2003.

Downey made his acting comeback in the 2003 film The Singing Detective, after Mel Gibson paid his insurance bond because completion bond companies would not insure him, and went on to star in the black comedy Kiss Kiss Bang Bang (2005), the thriller Zodiac (2007) and the action comedy Tropic Thunder (2008). Downey gained global recognition for starring as Iron Man in ten Marvel Cinematic Universe (MCU) films, from Iron Man (2008) to Avengers: Endgame (2019). He also played Sherlock Holmes in Guy Ritchie's Sherlock Holmes (2009), which earned him his second Golden Globe, and in its 2011 sequel.

Downey has also taken on dramatic parts in The Judge (2014) and Oppenheimer (2023), winning an Academy Award, a Golden Globe, and a BAFTA Award for Best Supporting Actor for his portrayal of Lewis Strauss in the latter. He was nominated for a Primetime Emmy Award for playing multiple characters in the black comedy miniseries The Sympathizer (2024). He debuted on Broadway that year, playing the title role in Ayad Akhtar's McNeal.