Mathilde Dorothy (Dolly) de Rothschild, née Pinto, was born in London to a well-to-do British family with large landholdings in Egypt. Her maternal grandfather, Levi Cohen, had been one of the founders of the Liberal Synagogue in London. She was educated at home and grew up speaking fluent French. In 1913, nearly age 18, she married James Armand de Rothschild, 17 years her senior, of the Paris branch of the Rothschild family. In 1922, her husband inherited Waddesdon Manor in Buckinghamshire, which became their country home. She was active in her husband's political life, including from 1929 to 1945, when he was a Liberal Member of Parliament, while serving as a member of the Buckinghamshire County Council and a Justice of the Peace in the Aylesbury law courts. During World War II, she held an important position in the Civil Defense, for which she was later awarded the MBE. After her husband's death, she continued his support for science, art and culture in Israel and Jews in other countries, and funded the construction of both the Knesset and the Supreme Court buildings.