Frontiere, who remained the Rams' majority owner and chairwoman for 28 years, died at UCLA Medical Center, where she had been hospitalized for several months with breast cancer, the team announced.
In a list of NFL team valuations compiled by Forbes magazine last September, the Rams were worth $908 million, ranking them 22nd among the league's 32 teams.
Few owners in sports have been as colorful and controversial as Frontiere, a vivacious, eccentric St. Louis native who married seven times, fired her stepson from the Rams' front office, loved music, embraced astrology, wrote poetry and withstood years of criticism that she was unfit to run a pro football team.
Yet "Madame Ram," as some called her, stood apart for nearly three decades as a rare female in the testosterone-charged National Football League. Her teams played in the Super Bowl three times, winning once, after the 1999 season.
Frontiere inherited control of the Rams when her sixth husband, longtime NFL owner Carroll Rosenbloom, drowned at age 72 while swimming off Florida in April 1979.
That Rosenbloom's will left the team to Frontiere surprised many in the sports world, but not Frontiere.
"I know what Carroll wanted," she said at the time. "Carroll knew he'd live through me. I was ready for [being the owner], but apparently a lot of other people weren't."
Frontiere was at times whimsical and theatrical but also could be forceful and resolute, especially when it came to managing the Rams.
In her early years as owner, Frontiere gave her players victory pecks on the cheek, introduced them to yoga and once handed out Cabbage Patch dolls for them to give to their children for Christmas.
She also made some unpopular front-office moves. Shortly after inheriting the franchise, she fired her well-respected stepson, Steve Rosenbloom, the Rams' operations manager, who had been groomed since childhood to run the team.
Each move raised eyebrows -- initially "she didn't know how to be an owner," former Rams quarterback Pat Haden once said -- and resurrected questions about her abilities as an NFL leader.
Even her last marriage, to composer Dominic Frontiere, brought controversy when he went to prison for a ticket-scalping scandal involving the Rams in the 1980 Super Bowl.
The pair divorced in 1988, but she kept his last name. She had spent the last 19 years with her companion, Earle Weatherwax, and maintained homes in Malibu, St. Louis and Sedona, Ariz.
By the early 1990s, negative media coverage prompted Frontiere, who initially enjoyed the spotlight as the Rams' boss, to turn publicity-shy and decline most interview requests. That's when criticism reached a fever pitch because she had moved the team to her hometown.
Frontiere felt she had little choice but to move the club from Anaheim, where it had played after leaving the Los Angeles Coliseum in 1980. The franchise no longer was self-supporting financially, it was struggling on the field, fan support was waning and, she believed, government officials had little interest in helping build a new stadium or take other steps that would boost revenue.
She could have sold the Rams to a local owner to keep the team in Southern California but opted to retain control and relocate to St. Louis, which had offered lucrative incentives to bring the team east, including $20 million in annual profits from guaranteed season-ticket sales and personal seat licenses as well as a favorable lease at a $280-million domed stadium.
"My grandmother had a saying: 'Go little where wanted, go not at all where little wanted,' " Frontiere said after NFL owners approved her move from Anaheim, where her late husband had decided to move in 1978 in search of luxury suites that the Coliseum lacked.