The iconic talk show host has been dating businessman Stedman Graham since 1986, but the pair has chosen not to go down the traditional path of marriage.
"It's not because I never had time — if I wanted to get married, I could've made the time," she told host Lorraine Kelly. "I'm not a traditional woman and I haven't had a traditional life, and I think that had Stedman and I gotten married, we certainly wouldn't have stayed married.
"If you were to ask him, he would say the same thing… He's a pretty traditional man. I've taught him to be non-traditional. But the very idea of what it means to be a wife and the responsibility and sacrifice that carries — I wouldn't have held that very well."
The 59-year-old is appearing on Lorraine as part of a two-part special this Friday and Monday. She also revealed what she considers to be her biggest achievement.
"The show was the true love of my life — it took up all of my energy," the self-made billionaire said of The Oprah Winfrey Show, which ended in 2011 after 25 years on air.
"For so many years I had that day job that occupied my whole life, so at the end of the Oprah show one of my final comments was “this show has been the love of my life”. That is absolutely the truth."