Walter John Matthau (October 1, 1920 – July 1, 2000) was an Academy Award-winning American actor best known for his role as Oscar Madison in The Odd Couple and his frequent collaborations with fellow Odd Couple star Jack Lemmon.

Born Walter Matthow on October 1, 1920, to a pair of Russian-Jewish immigrants in New York City, Matthau grew up poor on the Lower East Side and started out selling soft drinks and playing bit parts at a Yiddish theater at age 11. He was paid 50 cents for each of his occasional on-stage appearances. His father, a peddler from Kiev, left home when he was 3 years old. He lived with his older brother, Henry, and their mother, a garment worker, on the Lower East Side of New York. After graduating from Seward Park High School during the Depression, he took government jobs as a forester in Montana, a gym instructor for the Works Progress Administration and a boxing coach for policemen. During World War II, he served in the Army Air Corps as a radio cryptographer in a heavy bomber unit in Europe and returned home a sergeant with six battle stars. In 1948, his first Broadway role was when he was hired as an understudy for the role of an 83 year old English bishop in 'Anne of the Thousand Days' starring Rex Harrison (I). His fame came with Fortune Cookie, The (1966) and Odd Couple, The (1968). While making the former, he suffered a serious heart attack. This was due to heavy smoking and chronic gambling. Matthau immediately quit smoking and began a life-long regime of walking 2-5 miles per day. Unbeknownst to his fans, Matthau continued to battle heart disease and was later diagnosed with two forms of cancer. In 1976, he had heart bypass surgery. In 1993, he was hospitalized for double pneumonia. In 1995, he had a benign colon tumor removed. In 1999, he was hospitalized again for pneumonia. Matthau died on July 1, 2000. He was seventy-nine.