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LOS ANGELES — Barbara Sinatra, the fourth wife of legendary singer Frank Sinatra and a prominent advocate and philanthropist for abused children, has died at 90.

John Thoresen, director of the Barbara Sinatra Children's Center, says she died Tuesday of natural causes at her Rancho Mirage, California, home.

Frank Sinatra and his wife Barbara pose backstage for photographers on November 19, 1995, at the Shrine Auditorium in Los Angeles after the taping of "Sinatra: 80 Years My Way." Kevork Djansezian / AP file

A former model and Las Vegas showgirl, Barbara Sinatra was a prominent Palm Springs socialite in her own right before she married Sinatra in 1976.

They remained wed until his death in 1998.

Together they founded the center that bears her name.

The nonprofit has provided therapy to more than 20,000 young victims of physical, sexual and emotional abuse since opening in 1986.

Thoresen says Sinatra remained active at the center until recently, raising funds and visiting with the children.