Actor. Initially a character performer, he rose to leading man status during the 1960s-1970s, as he played a wide variety of roles from villains to gruff but lovable characters. He co-starred with Jack Lemmon in several pictures and became associated with playwright Neil Simon's works. Born Walter Matuschanskavasky, to Russian-Jewish immigrants, he was raised in New York City's Lower East Side. His first experience in acting was a small part in a Yiddish theater play, which was followed by his participation in high-school stage productions.

During World War II, Matthau saw active service as a radioman-gunner on a Consolidated B-24 Liberator bomber in the U.S. Army Air Forces with the Eighth Air Force based at RAF Old Buckenham in England. He flew 25 combat missions as a radioman and gunner on a B24 Liberator. He was decorated with the Air Medal in addition to numerous other honors, including six battle stars. He was nicknamed "Kid Reliable" by the others because of his steady nerves and composure under fire. 

He was with the same 453rd Bombardment Group as James Stewart. While based in England at RAF Old Buckenham, Norfolk, he flew missions to continental Europe during the Battle of the Bulge. He ended the war with the rank of Staff Sergeant and returned home to America for demobilization at the end of the war, intent on pursuing a career as an actor.

Following service as a radioman and gunner aboard a bomber with the United States Army Air Forces during World War II (WWII), he enrolled at the Dramatic Workshop of the New School for Social Research in New York City and studied under legendary theater director Erwin Piscator. He acquired experience in summer stock productions and marked his Broadway debut in the production "Anne of a Thousand Days" (1948). He made his motion picture debut in the film "The Kentuckian" (1955) and followed this over the next five years with "King Creole" (1958), "Gangster Story" (1959), and "Strangers When We Met" (1960). On Broadway, Matthau continued to build his star status as he appeared in "Guys and Dolls" (1955) and "Will Success Spoil Rock Hunter?" (1955). He received a Tony Award nomination for "Once More with Feeling" (1958) and earned a Tony Award for "A Shot in the Dark" (1961). Matthau received a second Tony Award for his origination of the character 'Oscar Madison' in Neil Simon's "The Odd Couple" (1965) and repeated the role in the 1968 movie adaptation in which he co-starred with Jack Lemmon. He shared the screen with Lemmon in Billy Wilder's "The Fortune Cookie" (1966) and received an Academy Award for Best Supporting Actor. During the filming of the movie, he suffered a massive heart attack. After this event, he decided to cut down on his stage performances and focus fully on films that he believed were less strenuous. He received further Oscar nominations for "Kotch" (1971) and "The Sunshine Boys" (1975). Matthau showed great versatility and experienced his most successful decade during the 1970s with such films as "A New Leaf" (1971), "Plaza Suite" (1971), "Pete 'n' Tillie" (1972, co-starred with Carol Burnett), "Charley Varrick "(1973), "The Laughing Policeman" (1974), "The Taking of Pelham One, Two, Three (1974), "The Bad News Bears" (1976) and "House Calls" (1978). Among his other pictures were "Lonely Are the Brave" (1962), "Charade" (1963), "Fail Safe" (1964), "Ensign Pulver" (1964), "Mirage" (1965), "A Guide for the Married Man" (1967), "Hello, Dolly!" (1968), Cactus Flower" (1969), "The Front Page" (1974), "Buddy Buddy" (1981), "I Ought to Be in Pictures" (1982), "The Survivors" (1983), "Pirates" (1986), "JFK" (1991), "Dennis the Menace" (1993), "Grumpy Old Men" (1993), "I.Q." (1994), "Grumpier Old Men" (1995), "Out To Sea" (1997), and "The Odd Couple II" (1998). Matthau received a star on the Hollywood Walk of Fame in 1982, located at 6357 Hollywood Blvd. He died from heart-related issues and is buried at Westwood Memorial Park, not far from his longtime co-star and friend Lemmon. He is the father of actor-director Charlie Matthau and stepfather of Lucy Saroyan, who is the daughter of playwright William Saroyan.