O'Neill was born in Rio de Janeiro, Brazil. Her mother was English and her father was a Brazilian of Portuguese, Spanish and Irish ancestry. She and her older brother Michael were raised in New Rochelle, New York, and Wilton, Connecticut. When she was 14, the family moved to New York City. On Easter Sunday, 1962, O'Neill attempted suicide because the move would separate her from her dog Mandy and horse Monty — "her whole world". That same year, she was discovered by the Ford modeling agency. By age 15, while attending the prestigious Dalton School in Manhattan, she was appearing on the covers of Vogue, Cosmopolitan, and Seventeen, earning $80,000 a year in 1962.
An accomplished equestrienne, O'Neill won upwards of 200 ribbons at horse show competitions in her teens. With her modelling fees, she had purchased a horse, named Alezon. However, it once balked before a wall at a horse show, throwing her, and breaking her neck and back in three places. She attended New York City's Professional Children's School and the Dalton School in Manhattan, but dropped out to wed her first husband, IBM executive Dean Rossiter, at age 17.
O'Neill has dual citizenship, as she maintained her Brazilian citizenship, being then a Brazilian and American citizen.
In 1968 O'Neill landed a small role in For Love of Ivy. In 1970 she played one of the lead female roles in Rio Lobo, starring opposite John Wayne.
She is most remembered for her role in the 1971 film Summer of '42, where she played Dorothy Walker, the young wife of an airman who has gone off to fight in World War II. She stated in a published 2002 interview that her agent had to fight to even get a reading for the part, since the role had been cast for an "older woman" to a "coming of age" 15-year-old boy, and the director was only considering actresses over the age of thirty, Barbra Streisand being at the top of the list.
O'Neill continued acting for the next two decades. She appeared in The Carey Treatment (1972), Lady Ice (1973), The Reincarnation of Peter Proud (1975), Sette note in nero (1977), Caravans (1978), A Force of One (1979), Scanners (1981), and The Cover Girl Murders (1993 made-for-television film). She went to Europe in 1976 and worked with Italian director Luchino Visconti, appearing in his last film, The Innocent (1976), where she played the part of the mistress, Teresa Raffo.
In 1982, O'Neill starred in the short-lived NBC prime time soap opera Bare Essence. She portrayed a role previously played by actress Linda Evans in the miniseries on which the soap was based. She was initially reluctant to star in a television series, because in those days actors usually only starred in either movies or on television. Her attitude changed when TV miniseries such as Rich Man, Poor Man and Roots started featuring film stars. When the movie business went into a doldrum, she agreed to star in two television movies, which she enjoyed, and then took on the starring role in Bare Essence. In 1984, she played the lead female role on the CBS television series Cover Up.
O'Neill is also listed in the Smithsonian Institution's National Museum of American History's Center for Advertising History for her long-standing contract with CoverGirl cosmetics as its model and spokesperson in ads and television commercials.
O'Neill has been married nine times to eight husbands (she married, divorced, and remarried her sixth husband). She has three children from three fathers.Dean Rossiter (1965 - 1971) (divorced) (1 child)
Joseph Koster (1972 - 1974) (divorced)
Nick De Noia (1975 - 1976) (divorced)
Jeff Barry (1978 - 1979) (divorced)
John Lederer (1979 - 1983) (divorced) (1 child)
Richard Alan Brown (1986 - 1989) (divorced) (1 child)
Neil L. Bonin (1992 - 1993) (annulled)
Richard Alan Brown (1993 - 1996) (divorced)
Mervin Sidney Louque, Jr. (1996 – present)
On October 23, 1982, O'Neill suffered a gunshot wound in her home on McClain Street in Bedford, New York. Police officers who interviewed OherNeill determined that she had accidentally shot herself in the abdomen with a .38 caliber revolver at her 30-acre, 25-room French-style estate while trying to determine if the weapon was loaded. Her fifth husband at the time, John Lederer, was not in the house when the handgun was discharged, but two other people were in the house. Detective Sgt. Thomas Rothwell was quoted as having said that O'Neill "didn't know much about guns."
On October 12, 1984, O'Neill's co-star in the Cover Up television series, Jon-Erik Hexum, accidentally shot himself on the show's set with a gun loaded with a blank cartridge. He died six days later.
In her 1999 autobiography Surviving Myself, O'Neill describes many of her life experiences, including her marriages, career, and her move to her Tennessee farm in the late 1990s. She has said that she wrote the autobiography (her first book) "... at the prompting of her children."
In 2004, O'Neill wrote and published From Fallen To Forgiven, a book of biographical notes and thoughts about life and existence. The actress, who underwent an abortion after the divorce from her first husband while dating a Wall Street socialite, became a pro-life activist and a born-again Christian in 1986 at age 38, counseling abstinence to teens. Concerning her abortion, she writes:
I was told a lie from the pit of hell: that my baby was just a blob of tissue. The aftermath of abortion can be equally deadly for both mother and unborn child. A woman who has an abortion is sentenced to bear that for the rest of her life.
O'Neill continues to be active as a writer working on her second autobiography, CoverStory, an inspirational speaker, and fundraiser for the benefit of crisis pregnancy centers across the United States. She has also served as the spokesperson for the Silent No More Awareness Campaign, an organization for people who regret that they or their partners had abortions.
O'Neill works for other charitable causes, such as Retinitis Pigmentosa International and the Arthritis Foundation. As a breast cancer survivor she was once a spokesperson for the American Cancer Society. She hosted a one-hour television special for World Vision International shot in Africa concerning the HIV epidemic. She sponsors the Jennifer O'Neill Tennis Tournament to benefit the American Society for the Prevention of Cruelty to Animals (ASPCA), and a fund-raiser for Guiding Eyes for the blind.Surviving Myself, New York: William Morrow and Company, 1999.
From Fallen to Forgiven, Thomas Nelson, 2002.
You're Not Alone: Healing Through God's Grace After Abortion. Faith Communications, 2005.
Remarkable Women, Insight Publishing Group, 2005.
A Fall Together, B&H Publishing Group, 2006.
A Winter of Wonders, B&H Publishing Group, 2007.
A Late Spring Frost, B&H Publishing Group, 2007
Faith Lessons, Insight Publishing Group, 2008.