Her family confirmed Summer's death, saying in a statement that they "are at peace celebrating her extraordinary life and her continued legacy."
"Words truly can't express how much we appreciate your prayers and love for our family at this sensitive time," the statement continued.
A onetime backup singer for Three Dog Night, Summer, who was born LaDonna Gaines, hit the American charts with the sexually charged "Love to Love You Baby," released in 1975 amid controversy that it was too steamy for radio. The song gained popularity, though, and became a huge favorite in discotheques.
The five-time Grammy winner went on to release a string of dance-friendly songs whose overt sexuality clashed with Summer's strict Christian upbringing in a family of seven children in Boston.
"I Feel Love" became a top 10 single in 1977 and her disco interpretation of the ballad "MacArthur Park" in 1978 was her first number one song. "Last Dance" from the Thank God It's Friday soundtrack earned Summer her first Grammy.
The singles "Bad Girls" and "Hot Stuff" from her prostitution-themed concept album – Summer poses as a hooker on the cover – both hit number one, as did her duet "No More Tears (Enough is Enough)" with Barbra Streisand.
But as Summer sang hit after hit she struggled with her meteoric fame and the fast life. She battled depression and anxiety, suffered an addiction to prescription medication and attempted suicide.
Fotos International / Getty
As disco waned at the end of the 1970s, so did Summer's career in the United States, though she continued to have modest success in Europe and scored occasional hits on the U.S. dance and R&B charts.
Her marriage to actor Helmuth Summer, which produced a daughter, collapsed in the mid-1970s. She later married singer Bruce Sudano, and the couple had two children, also daughters. According to the AP, the two were living together in Englewood, Fla.
After a nervous breakdown in 1979, Summer became a born-again Christian and rejected some of her more risqué songs, refusing to perform "Love to Love You Baby" until as late as last year, when she re-recorded it – complete with the moans – for a fragrance ad.
She released her final album, Crayons, in 2008 – her first studio recording in 17 years.
According to TMZ.com, which first reported her death, the singer was battling cancer.