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

Cooper died Wednesday morning in her sleep, her son the actor Corbin Bernsen wrote on Facebook. The family confirmed the death to CBS, according to a network spokeswoman.

She was in a Los Angeles-area hospital, according to Bernsen’s spokesman, Charles Sherman, who said the cause of death was not immediately available.

“One of the last great broads in our business — Jeanne Cooper, Mom — is now stirring up trouble in great beyond,” her family said in a statement.

Cooper will be remembered “as a daytime television legend and as a friend who will truly be missed by all of us here at the network,” said Nina Tassler, president of CBS Entertainment, adding that the actress brought “indelible charm, class and talent to every episode.”

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

“The Young and the Restless” has topped the daytime serial ratings for more than 24 years, in part because of the continuity provided by Cooper and its other longtime stars. It held its ground as the genre diminished in popularity and the majority of soaps vanished.