A leading actor (also leading actress) or Lead plays the role of the protagonist in a film or play. The word "lead" may also refer to the largest role in the piece and leading actor may refer to a person who typically plays such parts or an actor with a respected body of work. Many actors are typecast as "Leads" (this was particularly true of the Hollywood Studio system) but most may play the lead in some performances and supporting or character roles in others.
Sometimes there is more than one significant leading role in a dramatic piece, and the actors are said to play co-leads; a large supporting role may be considered a secondary lead. This is evidenced in the determining of categories in which actors are nominated for awards; sometimes two actors in the same performance piece are nominated for Best Actor; in 1935 Clark Gable, Charles Laughton and Franchot Tone were all nominated for the Academy Award for Mutiny on the Bounty (which was won by Victor McLaglen for The Informer.
There may be disagreement or uncertainty over whether a particular actor's work should be nominated in the Best Actor or Best Supporting Actor category. In 2008 Cate Blanchett has been nominated in both categories for I'm Not There