Variety reported Bacall suffered a suspected stroke.
The actress, known for her throaty voice and seductive stare, made her screen debut opposite Bogart at age 19 in "To Have and Have Not."
After seeing her in that film, director Billy Wilder referred to Bacall as "the girl with 'the look,'" and the phrase stuck.
Bogart was married at the time he met Bacall, and, within months, divorced his wife. The couple married in 1945 and co-starred in three more films, "The Big Sleep," "Dark Passage", and "Key Largo."
Bogart died of lung cancer in 1957 and in 1961 Bacall married actor Jason Robards, Jr. They divorced in 1969.
Bacall, who was born Betty Joan Perske, later shone on stage as well, starring in "Cactus Flower" and winning Tonys for "Applause" and "Woman of the Year."
In 1978 she published an autobiography, "By Myself."
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