Morgan was born Simone Renée Roussel[2] in Neuilly-sur-Seine, Hauts-de-Seine, a wealthy suburb of Paris.

[3][5] She took acting lessons from René Simon while serving as an extra in several films to pay for her drama classes.

[3] Morgan was first noticed by director Marc Allégret, who offered her a major role in the film Gribouille (1937), opposite Raimu.

[3] Upon the invasion of France in 1940 by the Germans, Morgan left for the United States and Hollywood where she was contracted to RKO Pictures in 1941.

[4] She was tested and strongly considered for the female lead in Casablanca but RKO would not release her for the amount of money that Warner Bros.

[3] Her other films from this period include; Carol Reed's The Fallen Idol (1948), Fabiola (1949), The Proud and the Beautiful (1953) by Yves Allégret, Les Grandes Manœuvres (1955) by René Clair and Marie-Antoinette reine de France (1956).

[4] In the 1970s, she virtually retired from her acting career, then made only occasional appearances in film, television and theatre.

[4] For her contribution to the motion picture industry, Morgan has a star on the Hollywood Walk of Fame at 1645 Vine Street.