Yancey died Jan. 26 at Olympia Medical Center in Los Angeles due to complication of pneumonia at age 96, her daughter, Gwen Adair, told the Los Angeles Times.
Yancey moved to Los Angeles from Tucson, where she also had a restaurant.
"I settled on hamburgers because they were the fastest-selling sandwich in America," she told the Wave newspaper in 1985.
Yancey, who was black, partnered with Charles Simpson to build a three- stool hamburger stand on Western Avenue near Jefferson Boulevard. It opened in in 1947 under the banner "Mr. Fatburger."
"The name of the store was my idea," Yancey said. "I wanted to get across the idea of a big burger with everything on it . . . a meal in itself."
From the beginning, Yancey was a fixture at the original Fatburger, where customers, who included entertainers such as Redd Foxx and Ray Charles, could custom-order their burgers.
"I worked 16, 17 and 18 hours a day behind the counter, seven days a week," Yancey recalled in the 1985 interview. "I'd come home, catch a few hours of sleep and start all over again."
Adair said her mother "was always there to make sure things were done properly. Even when she was older, she'd sit and talk to the people. That was her life; she loved being around the business."
In 1973, Yancey opened a Fatburger on La Cienega Boulevard in Beverly Hills, and it became a favorite destination for celebrity burger buffs.
Over the years, Fatburger has been immortalized in a string of songs, movies and TV shows, including the sitcom "Sanford and Son," the film "The Fast and the Furious" and the Ice Cube single "It Was a Good Day."
In 1981, Yancey began offering franchises in what was billed as "The Last Great Hamburger Stand."
By 1985, in addition to four company locations, there were 15 Fatburger franchise sites.
For three consecutive years, beginning in 1985, Fatburger was named in Entrepreneur magazine's annual Franchise 500 list.
Yancey sold her Fatburger company to an investment group in 1990 but retained control of the original property on Western Avenue. The stand was never designated as a Los Angeles historical-cultural monument and last year sold to a developer, The Times reported.
Santa Monica-based Fatburger Corp., owned by Fog Cutter Capital Group, currently has 93 locations in the United States, Canada and Macao.
Yancey, who was born in Texas on Jan. 3, 1912, established a $1.7- million endowment at City of Hope National Medical Center in Duarte in 1986 for research into sickle-cell anemia.
This was in fulfillment of a promise to her 22-year-old grandson, Duran Farrell, who died of the disease in 1983.
In addition to her daughter, Yancey is survived by three grandchildren and five great-grandchildren.