Eli Herschel Wallach (/ˈiːlaɪ ˈwɒlək/ EE-ly WOL-ək; December 7, 1915 – June 24, 2014) was an American film, television, and stage actor from New York City. Known for his character actor roles, his entertainment career spanned over six decades. He received a BAFTA Award, a Tony Award, and a Primetime Emmy Award. He also was inducted into the American Theater Hall of Fame in 1988 and received the Academy Honorary Award in 2010.

Originally trained in stage acting, he garnered over 90 film credits. He and his wife Anne Jackson often appeared together on stage, eventually becoming a notable acting couple in American theater. Wallach initially studied method acting under Sanford Meisner and later became a founding member of the Actors Studio, where he studied under Lee Strasberg. He played a wide variety of roles throughout his career, primarily as a supporting actor. He won the Tony Award for Best Supporting or Featured Actor in a Play for The Rose Tattoo (1951).

For his debut screen performance in Baby Doll (1956), he won a BAFTA Award for Best Newcomer and a Golden Globe Award nomination. Among his other most famous roles are Calvera in The Magnificent Seven (1960), Guido in The Misfits (1961), Tuco ("The Ugly") in The Good, the Bad and the Ugly (1966) and Don Altobello in The Godfather Part III (1990). Other notable films include How the West Was Won (1962), Tough Guys (1986), The Two Jakes (1990), The Associate (1996), The Holiday (2006), Wall Street: Money Never Sleeps, and The Ghost Writer (both 2010). He received Primetime Emmy Award nominations for Studio 60 on the Sunset Strip (2007) and Nurse Jackie (2011).

Eli Herschel Wallach (Yiddish: עלי הערשל וואלך) was born on December 7, 1915, at 156 Union Street in Red Hook, Brooklyn, a son of Polish Jewish immigrants Abraham (Yiddish: אברהם וואלאך) and Bertha Wallach (née Schorr; Yiddish: בערטה שורר וואלאך) from Przemyśl. He had a brother and two sisters. He and his family were among only a few Jews in an otherwise Italian American neighborhood. His parents owned Bertha's Candy Store. Wallach graduated in 1936 from the University of Texas with a degree in history. In a later interview, Wallach said that he learned to ride horses while in Texas, explaining that he liked Texas because "It opened my eyes to the word friendship... You could rely on people. If they gave you their word, that was it ... It was an education."

Two years later he earned a master of arts degree in education from the City College of New York. He gained his first method acting experience at the Neighborhood Playhouse School of the Theatre in New York City, where he studied under Sanford Meisner. There, according to Wallach, actors were forced to "unlearn" all their physical and vocal mannerisms, while traditional stage etiquette and "singsong" deliveries were "utterly excised" from his classroom.

Wallach's education was cut short when he was drafted into the United States Army in 1940. He served as a staff sergeant and medic in a military hospital in Hawaii and later was sent to Officer Candidate School (OCS) in Abilene, Texas, to train as a medical administrative officer. Commissioned as a second lieutenant, he was ordered to Casablanca. Later, when he was serving in France, a senior officer noticed his acting career and asked him to create a show for the patients. He and his unit wrote a play called Is This the Army?, which was inspired by Irving Berlin's This Is the Army. In the comedy, Wallach and the other actors mocked Axis dictators, with Wallach portraying Adolf Hitler. Wallach was discharged as a captain following the war's end in 1945. He was awarded the Army Good Conduct Medal, the American Defense Service Medal, the American Campaign Medal, the Asiatic–Pacific Campaign Medal, the European–African–Middle Eastern Campaign Medal and the World War II Victory Medal.

Wallach took classes in acting at the Dramatic Workshop of the New School in New York City with the influential German director Erwin Piscator. He later became a founding member of the Actors Studio, taught by Lee Strasberg. There, he studied more method acting technique with founding member Robert Lewis, and with other students including Marlon Brando, Montgomery Clift, Herbert Berghof, Sidney Lumet, and his soon-to-be wife, Anne Jackson. Wallach became Marilyn Monroe's first new friend when she became a student at the Actors Studio, once insisting on watching him perform in The Teahouse of the August Moon from the backstage wings, simply to see up close how experienced actors perform a two-hour play. She also became friends with his wife, Anne Jackson, also studying at the Studio, and would visit the couple at their home and sometimes babysit their new child.

In 1945 Wallach made his Broadway debut and he won a Tony Award in 1951 for his performance alongside Maureen Stapleton in the Tennessee Williams play The Rose Tattoo. His other theater credits include Mister Roberts, The Teahouse of the August Moon, Camino Real, Major Barbara (in which director Charles Laughton discouraged Wallach's established method acting style), Luv, and Staircase, co-starring Milo O'Shea, which was a serious depiction of an aging homosexual couple. He also played a role in a tour of Antony and Cleopatra, produced by the actress Katharine Cornell in 1946. He exposed Americans to the work of playwright Eugène Ionesco in plays including The Chairs and The Lesson in 1958, and in 1961 Rhinoceros opposite Zero Mostel. He last starred on stage as the title character in Visiting Mr. Green.