Douglas died on Thursday in Baton Rouge, Louisiana, near her hometown of Zachary.
The cause of death was pancreatic cancer, said her niece, Charlene Smith.
Douglas was 82.
She was best known for her role in The Beverly Hillbillies, the CBS comedy about a backwoods Ozark family who moved to Beverly Hills after striking it rich from oil discovered on their land.
As Elly May, she seemed blissfully unaware of her status as a bumpkin blonde bombshell.
Typically she was clad in a snug flannel shirt and tight jeans cinched with a rope belt, and she seemed to prefer her critters to any beau.
The show was not only assailed by critics, but by the network boss who put it on the air: “I hated it,” Michael Dann confided much later.
“After screening the pilot, I don’t think I ever watched another segment.”
The public, however, felt quite the opposite – it ran for nine seasons, often in the Top 10.