Helena Bonham Carter was born in Golders Green, in London. Her father was Raymond Bonham Carter, who came from a famous British political family; she is the great-granddaughter of the former Prime Minister of the United Kingdom, Herbert Henry Asquith, and members of her family are Life Peers. Her mother, Elena, was a psychotherapist. Her maternal grandfather was Eduardo Propper de Callejón, a Spanish diplomat and former Minister-Counselor at the Spanish Embassy in Washington, D.C.; her maternal grandmother, Helene Fould-Springer (who converted to Catholicism at marriage), was the daughter of a French-Jewish banker, Baron Eugene Fould, who was a friend of Marcel Proust (he took the surname Fould-Springer upon being made a Baron by Austrian Emperor Franz Joseph), and Mary ("Mitzi") Springer from an Austrian-based Jewish family, who were also the parents of the art patron Baroness Liliane de Rothschild (1916–2003), wife of Baron Elie de Rothschild.

Bonham Carter has two brothers, Edward and Thomas. Her father, who became ill when she was 10, suffered a stroke during an operation to remove a benign brain tumor, and was subsequently confined to a wheelchair. Bonham Carter was educated at the South Hampstead High School and Westminster School.

Bonham Carter's launch into the world of acting came in 1979, when she entered, and won, a national writing contest, and used the money won to pay for her entry into the actor's directory, "Spotlight".

It is a matter of interpretation what her film debut was. She made her professional acting debut at the age of 16, in a television commercial. She had a part in an obscure film A Pattern of Roses, but this is little remembered. Her first starring film role was in Lady Jane, which was eventually released to somewhat mixed reviews. Her breakthrough performance was in the role of Lucy Honeychurch in A Room with a View (1985), which was filmed after Lady Jane, but released first.

These early films led to her being typecast as a "corset queen", and "English rose", playing pre- and early 20th century characters, particularly in Merchant-Ivory films. However she eventually expanded her range, and now has a high profile for more recent films such as Fight Club, Tim Burton's Charlie and the Chocolate Factory, Corpse Bride and Big Fish, and Wallace & Gromit: The Curse of the Were-Rabbit.

In August 2001, Bonham Carter was featured in Maxim Magazine.

Bonham Carter will play Bellatrix Lestrange in Harry Potter and the Order of the Phoenix, which began filming in February 2006. She replaced Helen McCrory who left due to pregnancy.

She has been reluctant to discuss her private life, but some facts are generally known. She was in a relationship with actor Kenneth Branagh (with whom she appeared in several films), from 1994 to the summer of 1999. She then briefly dated actor Steve Martin. In October 2001, she began her current relationship with director Tim Burton, whom she met while filming Planet of the Apes. She has appeared in all of Burton's subsequent films, and the couple have a son, Billy-Ray Burton, born on October 4, 2003.

At one point she had to take out a court order against a man who had been stalking her, banning him from entering the large area around her home.