The larger-than-life character, who was known as an astrologer and wrestling promoter, "died in her sleep as she wished," said her youngest son, Frank.
"It was hard not to like her, she was a very eccentric and flamboyant person," he added in an Instagram post.
"Her mind was razor sharp until the day she died."
Born Jacqueline Frances Labofish on 29 November 1921, Stallone ran away from her home in Washington DC as a 15-year-old to join the circus.
"My father, who was a wealthy lawyer, wanted me to go to law school, but I wanted to be on stage," she told The Times in 2005.
She worked as a trapeze artist for two years before taking a job as a chorus girl on Broadway.
Stallone married her first husband Frank Stallone Sr, a hairdresser and occasional actor, in 1945. They remained together for 12 years and had two sons: Actor Sylvester and musician Frank.
She also had a daughter, Toni D'Alto, during her second marriage to Anthony Filiti. D'Alto died of lung cancer in 2012, at the age of 48.
A long-time advocate for women's fitness, she opened a female-only gym in the 1950s, called Barbella's, and presented an exercise slot on local TV in Washington, DC.
In the 1980s, she appeared on the wrestling programme GLOW: Gorgeous Ladies of Wrestling - which helped women's wrestling become mainstream on television. The origins of the organisation have recently been chronicled in the Netflix series Glow, starring Alison Brie and Betty Gilpin.
While her son Sylvester ascended to the Hollywood A-list through films like Rambo and Rocky, Stallone remained relatively low-profile, only becoming a household name in her own right in the 1990s, through her life-long passion for astrology.
In 1989, she wrote the book Star Power: An Astrological Guide to Supersuccess, and started to make regular TV appearances as an astrologer and psychic.
For a time, she ran her own psychic hotline, and also claimed to have invented the term "rumpology", which is the art of reading people's futures by reading the lines and crevices of their buttocks.