The hit show about a Yorkshire corner shop, which starred Ronnie Barker and Sir David Jason, ran in the 1970s and 80s before being revived in 2013.
Baron also appeared in EastEnders and the children’s show Come Outside.
Her agent said her “iconic roles” were “loved by all generations”, adding that she was “a leading light of our world”.
Baron told The Sunday Post in 2020 that although she loved playing Nurse Gladys and Auntie Mabel in Come Outside, she “couldn’t name my favourite of the different characters I have played”.
She told the newspaper: “Working with Ronnie Barker and David Jason was unbelievable – two great actors in a brilliantly scripted sitcom. There was never a day when we did not have a great laugh ourselves and that carried on when Still Open All Hours became a series.”
In Roy Clarke’s Open All Hours, she played the long-suffering Nurse Gladys, who resisted the amorous attempts of shop owner Albert Arkwright, played by Barker, to woo her.
Sir David played Arkwright’s equally long-suffering nephew, who went on to run the shop with his son when the show returned as Still Open All Hours in 2013.
Baron was nominated for a Bafta Award in 2011 for her role in The Road To Coronation Street, a one-off drama about the early days of the soap. She played actress Violet Carson, who portrayed Ena Sharples in the long-running series.
In BBC soap EastEnders, she played Linda Clarke, the mother of Jane Beale. She also appeared in Doctor Who, Last of the Summer Wine, Down To Earth, Dinner Ladies and Barbra Streisand’s 1983 film Yentl.
Her agent Donna French said: “It is with great sadness that we announce the passing of our beloved client Lynda Baron.
“She was a wonderful actress and a great friend. Her iconic roles of Nurse Gladys in Open All Hours and Aunt Mabel in Come Outside were loved by all generations.
“Renowned for her leading roles in West End musicals and dramatic productions alike, we have lost a leading light of our world.
“We extend our deepest condolences to her daughter Sarah, her son Morgan and all her family.”
Baron’s other credits included The Two Ronnies, 1970s sitcom Oh No, It’s Selwyn Froggitt, plus long-running drama The Bill and soap Crossroads and various Carry On films.