Canadian prima ballerina.

In 1954 Seymour went to England, where she danced with the Covent Garden Opera Ballet (1956) before joining the Royal Ballet in 1957, for which her creations include The Bride in Kenneth MacMillan's Le Baiser de la fée (1960) and The Girl in Les Deux Pigeons (1961). Although the role of Juliet in MacMillan's Romeo and Juliet was created for her, Dame Margot Fonteyn danced the premiere (1965).

In 1966 Seymour joined the German Opera Ballet in West Berlin, where she collaborated with MacMillan. Returning to the Royal Ballet, she enjoyed one of the greatest successes of her career in the principal role in Sir Frederick Ashton's A Month in the Country (1976). In 1978 Seymour became the artistic director of the Bavarian State Opera in Munich, but in early 1981 she left dance to begin a career in popular music.