Newton was born in Zambia, the daughter of Nyasha, a Zimbabwean health-care worker/nurse, and Nick Newton, a white English laboratory technician and artist.

Newton made her film debut in Flirting, (1991). This Australian movie was also a launch pad for a young Nicole Kidman, with whom she has remained friends. She gained international recognition opposite Nick Nolte in the Merchant-Ivory production of Jefferson in Paris as Sally Hemmings, which led to her being cast in Jonathan Demme’s Beloved (1998), in which she played the title character and costarred with Danny Glover, Kimberly Elise, and Oprah Winfrey. She played the female lead Nyah Hall in the film Mission: Impossible II.

Between 2003 and 2005, Newton played Makemba “Kem” Likasu, the love interest of Dr. John Carter on the American television series ER, and in 2004 also appeared in The Chronicles of Riddick. She appeared in Crash as a wealthy black woman who, along with her husband, finds herself the target of a racist policeman (played by Matt Dillon). The policeman molests her before ultimately saving her life. Newton was honoured with a BAFTA award for Best Supporting Actress in 2006. In 2005, Crash also won an Academy Award for Best Picture.

Newton is married to English writer and director Ol Parker, and they have two daughters: Ripley, born in 2000, and Nico, born in 2004.

In 2006, she contributed a foreword to We Wish: Hopes and Dreams of Cornwall’s Children, a book of children’s writing published in aid of the NSPCC. In it, she writes vividly about her childhood memories of growing up in Cornwall and the way in which the county’s vibrant cultural heritage made it easy for her to “enrich every situation with layers of magic and meaning”.

She also was encouraged to go “Green” when protesters bombarded her car with eggs at the gates of her daughters’ school. After that incident she swapped her BMW X5 for a Toyota Prius and wrote to her celebrity friends, asking them to join her in switching to more environmentally sound cars.