The media mogul was honoured for her philanthropy, and was introduced at the star-studded Governors Awards by a Harlem, New York student who earned a scholarship through the Oprah Winfrey Foundation.
Winfrey, a one-time Oscar nominee for her role in The Color Purple, was overcome with emotion following tributes from friends John Travolta and Maria Schriver and called the honour "unimaginable".
During her acceptance speech, she said, "The thank you comes from a place deeper than even I know... It's not just from me; it's from everybody who made me possible.
"What this really means is that all of us can make a difference through the life that we live."
Speaking at the event, longtime friend and mentor Sidney Poitier said, "I don't know of anyone who is more deserving."
As previously reported, James Earl Jones and make-up artist Dick Smith were also the recipients of honorary Oscars at the third annual Governors Awards.
The evening started on a light-hearted note as embattled Academy President Tom Sherak took to the stage dressed as Darth Vader, surrounded by Stormtroopers, as a tribute to Jones, who played the voice of the Star Wars villain.
Subtly acknowledging the resignations of Oscars co-producer Brett Ratner and host Eddie Murphy earlier in the week and the rush to fill their vacancies with Brian Grazer and Billy Crystal, respectively, he quipped, "How was your week?"