Eastwood began work as an actor, making brief appearances in B-films such as Revenge of the Creature, Tarantula and Francis in the Navy. In 1959, he got his first break with the long-running television series, Rawhide. As Rowdy Yates (whom Eastwood would later refer to in interviews as "the idiot of the plains"), he made the show his own and became a household name across the country.

Eastwood found lead roles as the mysterious “man with no name” in Sergio Leone's loose trilogy of westerns A Fistful of Dollars (1964), For a Few Dollars More (1965), and The Good, the Bad and the Ugly (1966). Although the first of these was evidently a tribute to Akira Kurosawa's Yojimbo, Leone used his innovative style to depict a wilder, more lawless and desolate world than traditional westerns. 

All three films were hits, particularly the third, and Eastwood became an instant international star, redefining the traditional image of the American cowboy (though his character was actually a gunslinger rather than a traditional hero). Also starred in Hang 'em High.

Stardom brought more roles, though still in the "tough guy" mold. In Where Eagles Dare (1968) he had second billing to Richard Burton but was paid $800,000. In the same year, he starred in Don Siegel's Coogan's Bluff, in which Eastwood was a lonely sheriff who came to the big city of New York to enforce the law in his own way. The film was controversial for its straightforward portrayal of violence, but it launched a more than ten-year collaboration between Eastwood and Siegel and set the prototype for the macho cop hero that Eastwood would play in the Dirty Harry series of films. 

In the next year Eastwood began to branch out. Paint Your Wagon (1969) was a western, but also a musical. Kelly's Heroes, (1970) combined tough-guy action with offbeat humor. In The Beguiled, directed again by Siegel, he played a villain. 1971 proved to be the biggest year yet for his career. He directed and starred in the thriller Play Misty for Me, but it was his portrayal of the hard-edged police inspector Harry Callahan in Dirty Harry that propelled Siegel's most successful movie at the box-office and arguably established Eastwood's most memorable character. The film has been credited with inventing the "loose-cannon cop genre" that is imitated to this day. 

Eastwood's tough, no-nonsense cop touched a cultural nerve with many who were fed up with crime in the streets. Dirty Harry led to four sequels: Magnum Force (1973), The Enforcer (1976), Sudden Impact (1983), and The Dead Pool (1988), as well as sparking numerous imitators such as Death Wish (1974), which had four sequels of its own.

Eastwood directed two important westerns during the revisionist '70s period in American film-making, High Plains Drifter (1973) and The Outlaw Josey Wales (1976).

In 1974, Eastwood teamed with a young actor named Jeff Bridges in Thunderbolt and Lightfoot. The movie was written and directed by Michael Cimino, who had previously written only the Dirty Harry sequel Magnum Force (and would win an Oscar for directing The Deer Hunter four years later). Critics and the public alike loved the chemistry between Eastwood and Bridges, making the film one of the biggest hits of 1974.

In 1975, Eastwood brought another talent to the screen: rock climbing. In The Eiger Sanction, in which he directed and starred, Eastwood - a 5.9 climber - performed his own rock climbing stunts. This film has become a cult classic in the rock climbing community. This film was done before the advent of CGI, so everything you see is real.

In 1979 Eastwood played another memorable role as the prison escapee Frank Morris in the fact-based movie Escape from Alcatraz. Morris was an escape artist who was sent to Alcatraz in 1960, which was, at the time, one of the toughest prisons in America. Morris devised a carefully thought out plan to escape from "The Rock" and, in 1962, he and two other prisoners broke out of the prison and entered San Francisco Bay. They were never seen again, and although the FBI believes that the escapees drowned, to this day their actual fate is unknown.

It was the fourth Dirty Harry film, Sudden Impact (1983), that made Eastwood a viable star for the '80s. President Reagan used his famous "make my day" line in one of his speeches. Eastwood revisited the western genre directing and starring in Pale Rider (1985), paying homage to the western film classic Shane which was rehearsed in the Cannes Film Festival and brought some hope to the dying Western after waterloo of Michael Cimino's Heaven's Gate. 

His fifth and final Dirty Harry movie, The Dead Pool (1988), was a success overall, but it did not have the box office punch his previous films had achieved. Eastwood alternated between more mainstream comedic films (if not particularly successful) such as Pink Cadillac (1989), and The Rookie (1990) and more personal projects, such as directing Bird (1988), a biopic of Charlie "Bird" Parker,which gave him the nomination for Golden Palm in the Cannes Film Festival and also starring in and directing White Hunter, Black Heart (1990), an uneven, loose biography of John Huston, which received some critical acclaim, although Katharine Hepburn contested the veracity of much of the material.

Eastwood rose to prominence yet again in the early 1990s. He directed and starred in the revisionist western Unforgiven in 1992, taking on the role of an aging ex-gunfighter long past his prime. The film, also starring such heavyweight actors as Gene Hackman, Morgan Freeman and Richard Harris, laid the groundwork for such later westerns as Deadwood by reenvisioning established genre conventions in a more ambiguous and unromantic light. A great success both in terms of box office and critical acclaim, it was nominated for nine Oscars, including Best Actor for Eastwood, and won four, including Best Picture and Best Director for Eastwood.

The following year, Eastwood played a guilt-ridden Secret Service agent in the thriller In the Line of Fire (1993) directed by Wolfgang Petersen. This film was a blockbuster and among the top 10 box-office performers in that year. Eastwood directed and starred with Kevin Costner in A Perfect World in the same year. He continued to expand his repertoire by playing opposite Meryl Streep in the love story, The Bridges of Madison County (1995). Based on a best-selling novel, it was also a hit at the box-office. 

Afterward, Eastwood turned to more directing work--much of it well received--including Midnight in the Garden of Good and Evil (1997), Mystic River (2003), and Million Dollar Baby (2004), but he also acted in the last of these and garnered another Best Actor nomination.