Legendary Actress Diane Keaton's Cause of Death Revealed

Diane Keaton’s cause of death has been revealed -- the legendary actress passed away from pneumonia.

Diane's family revealed the cause of death in a statement to PEOPLE, saying ... "The Keaton family are very grateful for the extraordinary messages of love and support they have received these past few days on behalf of their beloved Diane, who passed away from pneumonia on October 11."

The family added ... "She loved her animals and she was steadfast in her support of the unhoused community, so any donations in her memory to a local food bank or an animal shelter would be a wonderful and much appreciated tribute to her."

Diane died October 11 ... and as TMZ first reported, the L.A. Fire Dept. paramedics responded to her home around 8:08 AM Saturday, transporting one person -- confirmed by sources as Keaton -- to a nearby hospital.

Dispatch audio caught responders calling a "person down" at her address.

The icon is survived by her adopted children -- 25-year-old son, Duke, and 29-year-old daughter, Dexter.

She was 79.