Sandy Posey, 'Single Girl' Singer from 1960s, Dead at 80 After Dementia Battle

Sandy Posey -- who hit it big time in the '60s with her music career -- has died ... TMZ has learned.

The late pop singer's husband, Wade Cummins, tells us his wife passed away Saturday morning at her home in Tennessee -- this following complications from dementia, we're told.

Wade tells us Sandy had been battling dementia for a while now, with a slow decline over the past seven years. Aside from that, he says she was in relatively good health ... with no issues like high blood pressure or problems with any other organs.

We're also told Wade was by Sandy's bedside when she died ... along with her daughter Amy and their niece. Wade says he cared for her in her final years but is understandably heartbroken -- she was the love of his life, and he’s missing her deeply.

Wade acknowledges their close relationship with God, saying it brings him comfort knowing Sandy's now with Jesus. He also mentions Sandy had millions of fans worldwide .. and the outpouring of support from them has also been very comforting.

The family will host a celebration of her life at some point, but the family hasn’t set an official date yet. Wade says he plans to have it filmed live for Facebook so her fans can join in ... we're also told Sandy will be cremated.

Sandy was known for her string of hit singles throughout the '60s, such as "Born a Woman" and "Single Girl." Other songs of hers include "I Take It Back," "Bring Him Safely Home to Me," "What a Woman in Love Won't Do" and others.

She was signed to MGM, Columbia, Warner Bros. and other labels throughout her career. Sandy was 80.