Radziwill died of natural causes in her Manhattan home Friday, her daughter Anna Christina Radziwill, confirmed to.the New York Times.
The globe-trotting trendsetter was born Caroline Lee Bouvier on March 3, 1933, and during her lifetime she dabbled in Hollywood as an actress in the 1968 film Laura before becoming an interior designer. She went on to work for Giorgio Armani in roles including brand ambassador and public relations executive.
However, she would become admired for her sense of fashion, as noted by Vanity Fair's inclusion of her in its Best-Dressed List Hall of Fame.
Fashion designer Valentino Garavani told WWD, "It's a natural end of a marvelous life. She had everything a woman can desire...beauty, intelligence, style, fame... I am sure she had moments of happiness, too."
He also posted a photo of Radziwill with Onassis on Instagram, saying that they were now reunited.
Radziwill married and divorced three times, most notably to Polish aristocrat Prince Stanislaw Albrecht Radziwill.
The couple had two children together, including Anna Christina Radziwill and Anthony, who died of cancer in 1999.
Designer Tory Burch said she was "heartbroken" by her friend's passing.
"I will miss our dear friend. Rest In Peace, Lee Radziwill," she said.
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Notable deaths of 2019