The actress passed away Friday at her home surrounded by family, according to a lengthy post on her Instagram page ... but her cause of death was not revealed.

The sad IG announcement read in part ... "Olivia was a remarkable person whose warmth, wisdom, and pure kindness touched the lives of all who knew her."

Hussey won a Golden Globe for her portrayal of Juliet at just 15 years old in the Oscar-winning film opposite Leonard Whiting who portrayed Romeo.

However, the film was not without controversy ... as it depicted a nude Olivia and Leonard in one scene, when they both were under 18 years old during filming. The actors revived a lawsuit earlier this year against Paramount Pictures and Criterion Collections over the distribution of the scene, but it was dismissed in October.

In 2008, the actress was diagnosed with breast cancer and it went into remission after she had a mastectomy ... then in 2018 she told Express that new tumor surfaced.

Hussey is survived by her longtime husband David Glen Eisley, her three children Alex, Max and India and grandson Greyson.

She was 73.