Jeanne Cooper, the enduring soap opera star who played grande dame Katherine Chancellor for nearly four decades on “The Young and the Restless,” died May 8. She was 84.

The actor Corbin Bernsen, her son, announced her death on Facebook. She was in a Los Angeles area hospital, said Bernsen’s spokesman, Charles Sherman, who said the cause of death was not immediately available.

Ms. Cooper joined the daytime serial six months after its March 1973 debut, becoming its longest-tenured cast member. The role earned her 11 Daytime Emmy nominations and a trophy for best actress in a drama series in 2008.

“God knows it’s claimed a big part of my life,” she told the Associated Press in March as “The Young and the Restless” celebrated its milestone 40th anniversary.

As the years passed, Ms. Cooper brushed aside thoughts of saying goodbye to the show and its fictional Wisconsin town of Genoa City.

“What would I do?” she told the AP as she turned 83 in October. “I’m no good at crocheting. My fingers would bleed,”

On April 12, Bernsen tweeted that his mother faced an “uphill battle” for an undisclosed illness. In subsequent days, he wrote of her gradual improvement and said that she’d been taken off breathing equipment.

In a Facebook posting April 17, Bernsen said his mother cursed several times, “showing me that she’s becoming her old self, not thrilled about the situation, and ready to get out of the hospital and shake up the world.”

Wilma Jeanne Cooper was born Oct. 25, 1928, in Taft, Calif. She attended the College of the Pacific and performed in local theater productions before her professional career began with the 1953 film “The Redhead From Wyoming,” starring Maureen O’Hara. Other film credits include “The Boston Strangler” with Tony Curtis (1968) and “Tony Rome” with Frank Sinatra in 1967.

She had a parallel career in TV, with shows including “The Adventures of Kit Carson” in 1953 and “The Pepsi-Cola Playhouse” in 1954 and “Bracken’s World” in 1969-70.

In a recurring role on “L.A. Law,” Ms. Cooper played the mother of Bernsen’s character, Arnie, and received a 1987 Emmy nomination for best guest actress in a drama.

Bernsen later joined his mother on her series, making several appearances as a priest, Father Todd.

But it was her role on “The Young and the Restless” that made her a TV star intimately familiar to viewers.

In 1984, Ms. Cooper’s real-life facelift was televised on the show as her character underwent the surgery at the same time and had no regrets about it.

“It opened up reconstructive surgery for so many people, youngsters getting things done,” she said. “To this day, people will come up to me and say, ‘Thank you so much for doing that. My mom or I had something done, and not just cosmetic surgery.’ That was an incredible experience in my life.”

“The Young and the Restless” has topped the daytime serial ratings for more than 24 years, in part because of the continuity provided by Ms. Cooper and its other longtime stars, including Eric Braeden.

Ms. Cooper’s 30-year marriage to Harry Bernsen ended in divorce.

In addition to Corbin Bernsen, survivors include two other chilren, Caren Bernsen and Collin Bernsen; and eight grandchildren.

— Associated Press