Rampling was born in Sturmer, Essex, the daughter of Isabel Anne (née Gurteen), a painter, and Godfrey Rampling, an Olympic gold medalist and army officer. She attended Jeanne d'Arc Académie pour Jeunes Filles in Versailles and St. Hilda's School, a boarding school in Bushey, Hertfordshire, England.
One of the most traumatic events in Rampling's life occurred in 1966, when she was 20 years old. Her elder sister Sarah killed herself after giving birth prematurely and losing her child. Rampling was devastated by this loss, which she experienced as an abandonment by her sister. She and her father lied to her mother, telling her that Sarah had died of a stroke. Rampling seemingly overcame this trauma and was able to continue acting. Many years later she made a film in which her character was named Sarah.
In 1972, Rampling married the actor and publicist Bryan Southcombe. They were widely reported to be living in a ménage à trois with a male model, Randall Laurence. They had a son Barnaby Southcombe before divorcing in 1976. (He has become a successful television director.)
In 1974, Rampling was quoted by the syndicated columnist Earl Wilson as saying: "There are so many misunderstandings in life. I once caused a scandal by saying I lived with two men [...] I didn't mean it in a sexual sense [...] We were just like any people sharing a flat."
She has been engaged to Jean-Noël Tassez, a French communications tycoon, since 1998. On 6 April 2009, The Daily Mail reported that Rampling had hired lawyers to try to block the publication of a biography about her written by a close friend.
In March 2013, Rampling was listed by The Guardian as one of its "fifty best-dressed over 50s."