America's sweetheart of the '50s and '60s Doris Day has died aged 97, her foundation has confirmed.

The Doris Day Animal Foundation has released a statement saying that the late actress was in "excellent physical health for her age, until recently contracting a serious case of pneumonia."

Day was a household name for her roles in films from the Golden Age of Hollywood, such as Calamity and Pillow Talk, the latter which earned her an Academy Award nomination.

Despite never winning an Oscar, she awarded the Golden Globe Lifetime Achievement Award in 1989 and was given the President Medal of Freedom in 2004 by President George W. Bush.

After retiring from acting in 1975 she preferred a private life away from the public eye.

In her later years, she took an interest in animal activism and adopted the nickname "The Dog Catcher of Beverly Hills"  because of her efforts to reunite lost pets with their owners. Her ex-husband Barry Comden claimed she cared more about her animals than him.

In 2011 she released her first album in decades, My Heart, making her the oldest artist to record a UK Top 10 album.

In her autobiography Doris Day: Her Own Story, she wrote: "My public image is unshakably that of America's wholesome virgin, the girl next door, carefree and brimming with happiness, an image, I can assure you, more make-believe than any film part I ever played. But I am Miss Chastity Belt and that's all there is to it."

Tributes from others have poured in after news of Day's death.

For those of us in my generation, Doris Day was synonymous with Hollywood icon. She would no doubt remind us, upon this day of her passing, “Que sera sera,” but we will miss her dearly anyway. Rest now in our hearts forever, Ms. Day.

— George Takei (@GeorgeTakei) May 13, 2019

Farewell to the great Doris Day.
Here's the legendary actor and singer at the Hall in 1955, being directed by Alfred Hitchcock. She's about to spot a bad guy in our Door 6 porch, setting up the nerve-shredding finale of 'The Man Who Knew Too Much' 🎥 pic.twitter.com/yIuyZfldQc

— Royal Albert Hall (@RoyalAlbertHall) May 13, 2019

The actress celebrated her 97th birthday on 3 April.

Her foundation has stated that she does wish wish for "funeral or memorial service and no grave marker".