She was 97 and had been retired from Hollywood for more than half a century, having devoted the second half of her life to animal welfare causes. She was also nominated for a Best Actress Oscar in 1959 for her role in Pillow Talk, and was given a Lifetime Achievement Golden Globe Award in 1989.
"I've always said that age is just a number and I have never paid much attention to birthdays", Day said in a statement to The Hollywood Reporter.
BREAKING: Doris Day, whose wholesome screen presence stood for a time of innocence in '60s films, has died, her foundation says. She left the band a few years later to go solo, and went on to cut more than 650 songs over a 20-year period from 1947 to 1967. Everyone knows her megahit, "Que Sera, Sera", a sort of anthem about going whichever way the wind takes you, the ideal song to sing to a child who, in the way children are, is eager for all the answers. She took singing lessons and began appearing on local radio.
"Since the '70s, Day had focused her energies on the Doris Day Animal Foundation".
Her most famous songs, meanwhile, surely include the 1956 release of Que Sera, Sera (Whatever Will Be, Will Be).
Day received the the Presidential Medal of Freedom in 2004. "She had a heart of gold and was a very amusing lady who I shared many laughs with".
Two for Tea: A personal favorite of mine as it's all my grandparents used to sing, this song is from Day's film of the same name.
At 17, Day married Al Jorden, a trombone player who she later claimed beat her.
"With Six You Get Eggroll" was her last film in 1968.
The Doris Day Show: According to Justwatch.com, this sitcom originally broadcast on the CBS network from September 1968 until March 1973. Check out a great scene from Pillow Talk below. Melcher was the adoptive father of her only child - son Terry Melcher, who died of cancer in 2004.
Day did not learn until after Melcher's death that he had committed her to do the show and she was initially reluctant to do it.
Melcher famously worked with The Beach Boys and turned down aspiring musician Charles Manson.
Our thoughts are with her family and friends during this hard time.
Day married a fourth time at age 52, to businessman Barry Comden in 1976.