Dolly Parton -- Sorry Ladies, I'm NOT a Lesbian

Dolly Parton is NOT gay ... the same way that Oprah Winfrey is not gay ... so says Dolly Parton.

Dolly set the record straight about her sexual orientation during an interview with "Nightline." Parton says she's well aware of the rumors that she's in a secret relationship with her BFF Judy Ogle ... but claims the rumors are simply untrue.

"Judy and I have been best friends since we were like in the third and fourth grade," Parton explained ... saying, "We still just have a great friendship and relationship and I love her as much as I love anybody in the whole world, but we're not romantically involved."

In fact, Dolly -- who's been married to a man for 46 years -- says she bonded with Oprah over the lesbian rumors ... since Oprah has also been hounded by false rumors that she's in a secret relationship with her BFF Gayle King.

"Like Gayle, her friend, Judy, my friend ... [people] just think that you just can't be that close to somebody."