The Doris Day Animal Foundation confirmed Day died Monday of pneumonia at her Carmel Valley, California home.
Born Doris Mary Ann Kappelhoff on April 3, 1922, Day got her start in Hollywood as a big band singer who scored her first No. 1 hit with "Sentimental Journey" in 1945. On the strength of her voice, Day, who had no acting experience, was offered a starring role in 1948's Romance on the High Seas.
Day became one of the era's most prolific film actresses, starring in movie musicals like Lullaby of Broadway and Calamity Jane and dramas like Alfred Hitchcock's The Man Who Knew Too Much, for which she sang "Que Sera, Sera," which won an Academy Award for best original song. Day later starred opposite Clark Gable in 1958 comedy Teacher's Pet.
She was marketed as a wholesome girl next door, but the sunny blonde found the most success in roles that challenged her all-American reputation. Day earned her Oscar nomination opposite Rock Hudson in 1959 romantic comedy Pillow Talk, the first of three rom-coms they filmed together.
In her 1976 tell-all autobiography, Doris Day: Her Own Story, Day described her squeaky-clean reputation as "unfortunate." The Hollywood legend opened up in her book about her tumultuous personal life, divorces, and financial hardship.
From 1966 to 1973, Day starred as a widowed mother in CBS sitcom The Doris Day Show. She wrote in her autobiography that her husband at the time, Martin Melcher, had signed her on for the series without her knowledge, which she said she had discovered only after Melcher's death in 1968.
In her later years, Day was a committed activist for animal rights, founding what would become the Doris Day Animal Foundation in 1978.
She was given a Presidential Medal of Freedom in 2004.