American film actor and director known for his versatility and intense performances. He won an Academy Award for his role as a grief-stricken father of a murdered young woman in Mystic River (2003).

The son of show-business parents, Penn chose to forgo college and instead joined the Los Angeles Repertory Theater. After a few television appearances, including a role in an episode of Barnaby Jones (1979), he moved to New York City in 1980. Well-received performances in the Off-Broadway Heartlands and the film Taps (both 1981) paved the way for Penn's fame-making role as the underachieving surfer Jeff Spicoli in Fast Times at Ridgemont High (1982). He followed with a variety of roles that showcased his intensity and versatility—including a teenage delinquent in Bad Boys (1983), a punk rocker/burglar in Crackers (1984), a World War II Marine about to ship out in the romance Racing with the Moon (1984), and a spy selling U.S. government secrets to the KGB in The Falcon and the Snowman (1985)—garnering favourable notices from critics even when the vehicle he performed in was not as well liked. Penn's career took a downturn, however, during his relationship with pop star Madonna, whom he married in 1985. There were frequent confrontations with paparazzi, a number of them combative, and Penn spent a month in jail in 1987. The marriage ended in 1989—but not before the couple had costarred in Shanghai Surprise (1986), a film reviled by most critics.

Penn's subsequent movies did better, however, and he also branched out, writing and directing Indian Runner (1991) and directing The Crossing Guard (1995). He earned his first Oscar nomination for Dead Man Walking (1995), starring opposite Susan Sarandon (Sarandon, Susan) as a death-row inmate. He appeared with his second wife—Robin Wright Penn—in She's So Lovely (1997), for which he was named best actor at the Cannes film festival, and later garnered Oscar nominations for Sweet and Lowdown (1999) and I Am Sam (2001). Another impressive directorial effort came with The Pledge. The drama featured Jack Nicholson (Nicholson, Jack) as a police detective who vows to find a child killer. In 2003 Penn won the best actor honours at the Venice Film Festival for 21 Grams (2003), and the following year he received a best actor Oscar for his role in Mystic River.

Penn's later films include The Assassination of Richard Nixon (2004), based on an actual attempt on the president's life; The Interpreter (2005); and All the King's Men (2006), an adaptation of Robert Penn Warren's novel about a populist politician. Penn returned to directing with Into the Wild (2007). The film—based on Jon Krakauer's best-selling book of the same name—chronicles the journey of Christopher McCandless, an idealistic college graduate who repudiates materialistic society as he hitchhikes through the American West and ventures alone into the Alaskan wilderness. In 2008 Penn played the lead role in Milk, which chronicles the life of Harvey Milk (Milk, Harvey), one of the first openly gay elected officials in the United States. His ebullient portrayal of Milk earned him another Academy Award nomination for best actor.

Penn was a political activist, and he often attracted controversy for his stances, most notably his opposition to the U.S.-led Iraq War and his criticism of U.S. Pres. George W. Bush (Bush, George W.). In 2005 he participated in the recovery efforts in New Orleans following Hurricane Katrina (Katrina, Hurricane).