A supporting actor is an actor who performs roles in a play or film other than that of the leads.

These roles range from bit parts to secondary leads. They are sometimes but not necessarily character roles. A supporting actor must also use restraint not to upstage the main actor/actress in the play/movie. In earlier times these were often ethnic stereotypes. The title is usually specific to the performance, that is, a person may be a supporting actor in one film and the leading actor in the next. An individual who typically plays supporting roles is considered a character actor.

In television, a day player refers to most performers with supporting speaking roles hired on a daily basis without long-term contracts.

Supporting roles may be pivotal or vital to the story. In recognition of important nature of this work, the theater and film industries give separate awards to the Best Supporting Actor and actress. A supporting actor/actress can also be known as a 'sidekick'.

Heath Andrew Ledger (4 April 1979 – 22 January 2008) was an Australian television and film actor. After performing roles in Australian television and film during the 1990s, Ledger left his homeland for the United States in 1998 to develop his film career. His work comprised nineteen films, including 10 Things I Hate About You (1999), The Patriot (2000), A Knight's Tale (2001), Brokeback Mountain (2005), and The Dark Knight (2008). In addition to acting, he produced and directed music videos and aspired to be a film director.

For his portrayal of Ennis Del Mar in Brokeback Mountain, Ledger won the 2005 New York Film Critics Circle Award for Best Actor and the 2006 "Best Actor" award from the Australian Film Institute and was nominated for the 2005 Academy Award for Best Actor as well as the 2006 BAFTA Award for Best Actor in a Leading Role. Posthumously he shared the 2007 Independent Spirit Robert Altman Award with the rest of the ensemble cast, the director, and the casting director for the film I'm Not There, which was inspired by the life and songs of American singer-songwriter Bob Dylan. In the film, Ledger portrayed a fictional actor named Robbie Clark, one of six characters embodying aspects of Dylan's life and persona. Ledger received numerous accolades for his critically acclaimed portrayal of the Joker in The Dark Knight, including the Academy Award for Best Supporting Actor, a Best Actor International Award at the 2008 Australian Film Institute Awards, for which he became the first actor to win an award posthumously, the 2008 Los Angeles Film Critics Association Award for Best Supporting Actor, the 2009 Golden Globe Award for Best Supporting Actor and the 2009 BAFTA Award for Best Supporting Actor.

Jared Joseph Leto (born December 26, 1971) is an American actor, director, producer, musician, and occasional model. Leto has appeared in both big budget Hollywood films and smaller projects from independent producers and art houses. He rose to prominence for playing Jordan Catalano in the teenage drama My So-Called Life (1994). He later made his film debut in How to Make an American Quilt (1995) and received first notable critical praise for his performance in Prefontaine (1997). Leto played supporting roles in The Thin Red Line (1998) and Girl, Interrupted (1999), as well as the lead role in the horror film Urban Legend (1998), and earned critical acclaim after portraying heroin addict Harry Goldfarb in Darren Aronofsky's Requiem for a Dream (2000). He has worked with director David Fincher in Fight Club (1999) and Panic Room (2002). Since the 2000s, Leto has been nominated for awards for his work in such films as American Psycho (2000), Highway (2002), Lord of War (2005), Lonely Hearts (2006), Chapter 27 (2007), and Mr. Nobody (2009).