Fonda was born on December 21, 1937 in New York City. She is the daughter of actor Henry Fonda (1905–1982) and the Canadian-born socialite Frances Ford Seymour (1908–1950). According to her father, their surname comes from Italian ancestors who immigrated to the Netherlands. There they intermarried and began to use Dutch given names. She is also of English, Scottish, French-Canadian, German, and Norwegian ancestry. She was named after the third wife of English king Henry VIII, Jane Seymour. Her mother is distantly related to Jane Seymour. Her brother was actor Peter Fonda (1940–2019) and through him, her niece was his daughter Bridget. In 1950, her mother committed suicide when Jane was 13.