The 65-year-old Jenner made the declaration in a wide-ranging interview with ABC's Diane Sawyer, nearly 40 years after his record-breaking Olympic gold-medal win in the decathlon that gave him the unofficial title of "World's Greatest Athlete."
At the outset of the taped interview at Jenner's Malibu, California, house, Sawyer asked "Are you a woman?" and Jenner responded, "Yes, for all intents and purposes I am a woman."
"People look at me differently," Jenner added. "They can see you as this macho male, but my heart and my soul, and everything that I do in life, it is part of me, that female side is part of me. That's who I am."
Known to younger generations as the patriarch of reality TV's Kardashian clan, Jenner went on ABC's "20/20" to put to rest months of speculation that he was transitioning to life as a woman.
"I was not genetically born that way," Jenner said. "As of now, I have all the male parts and all that kind of stuff. In a lot of ways we are different, OK? But we still identify as female. And that's very hard for Bruce Jenner to say. Because why? I don’t want to disappoint people."
Although Jenner did not address pronoun preference, Sawyer said that for this interview, Jenner asked that the public use "the familiar 'him' or 'he'."
Three times married and divorced and parent to six biological children and four stepchildren, Jenner said he is not gay and has never had sex with a man.
His first two wives sent messages of support for Jenner to Sawyer, while his most recent wife, Kris Jenner, the manager and mother of the stars in E! Entertainment's "Keeping Up with the Kardashians" had no comment.
SUPPORT IN KARDASHIAN CLAN
One of the most difficult times for Jenner was around 18 months ago, when journalists were waiting for him as he went to undergo a tracheal shave, a sign of a transition to women. He briefly had thoughts of taking his own life to escape the glare of the sensationalist media.
Telling his family, however, of his transition went rather smoothly and Jenner's eldest children expressed their support for their father on camera.
"I feel like I am getting an upgraded version of my dad," said son Brandon Jenner.
Stepdaughter Kim Kardashian, perhaps one of the most famous of American reality TV stars, has been "by far the most accepting and the easiest to talk to," Jenner said. Her husband, rapper Kanye West, had been instrumental in helping her accept Jenner's transition, he added.
According to Jenner, Kim Kardashian encouraged him by saying "Girl, you gotta rock it baby. You gotta look good."
Khloe Kardashian, also a stepdaughter famous for the TV show, has had "the toughest time with it because she's had a lot of losses in her life," Jenner said.
The two youngest daughters, Kendall and Kylie Jenner, sent a message of support to the program saying "All we want is for him to be happy. If he's happy, we're happy."
Jenner was one of the most prominent athletes of the 1970s after he won the decathlon at the 1976 Summer Olympic Games in Montreal and broke the world record for points in the 10-event competition.
His life with the Kardashians and eight seasons on television gave him a second round of fame as cameras followed their every move.
"I had the story," Jenner said, referring to the secret that he kept under wraps until Friday.