Ghislaine Thesmar was born in 1943 in Beijing (China). She studied at the Paris Conservatoire. She danced with Ballet du Marquis de Cuevas (1961), Lacotte's company Ballet National des Jeunesses Musicales de France, Ballet Rambert, Petit's company Les Grand Ballets Canadiens, and then as Etoile with the Paris Opera Ballet from 1972 to 1985. She also appeared as a guest artist with New York City Ballet. She lead the Ballets de Monte-Carlo with her husband Pierre Lacotte from 1986 to 1988, and later taught at the Paris Opera Ballet.
She created roles in Formes (Petit, 1967), Catulli Carmina (Nault, 1969), Pas rompu (Nault, 1969),
La Sylphide (Taglioni, restaged by Lacotte, 1971), Schéhérazade (Petit, 1974) and La nuit transfigurée (Petit, 1976). Among her best roles were in Swan Lake, Giselle, Tudor's Lilac garden and Nijinska's Les Noces.