She was born in Brussels and her real name was Marguerite Antoinette Jeanne Marie Ghislaine Cleenwerck de Crayencour, and was given her father's French nationality although her parents were both from old Flemish families. When she started publishing poetry in her late teens, she created her pen-name, an anagram constructed with her father's help, and registered it as her legal name in the US in 1947.

Yourcenar wrote several novels and an influential essay on Yukio Mishima. She became the first and only woman to be admitted to the Académie Française in 1980. She moved to the USA at the outbreak of World War II.

She lived for 42 years with her lover, the American academian Grace Frick, whom she met in 1937, and with whom she was to live until Frick's death from breast cancer in 1979. Grace was the principal translator of Marguerite's works into English. Yourcenar was in the US in June 1940, when the Germans invaded France, and there she was to remain for most of her life, setting up house with Frick on the coast of Maine.

Of special interest are the yearly issues of the Bulletin Marguerite Yourcenar, devoted each time to one single theme in her life and works. She neither spoke of nor denied her sexuality, but it is an important fact of her work that she wrote constantly about male homosexual characters.