Elsa Schiaparelli

Elsa Schiaparelli,1932, by George Hoynignen-Huene, "What a neckline"

Source: closetcouture

Paul Poiret

Every decade has its seer or sybil of style, a designer who, above all others, is able to divine and define the desires of women. In the 1910s, this oracle of the mode was Paul Poiret, known in America as "The King of Fashion." Paul Poiret (20 April 1879, Paris, France – 30 April 1944, Paris) was a French fashion designer, French couturier, the most fashionable dress designer of pre-World War I Paris.

Source: benjaminkanarekblog | Library of Congress | Encyclopædia Britannica
 

Madeleine Vionnet

Madeleine in her studio 1920
Madeleine Vionnet ( June 22, 1876 – March 2, 1975) was a French fashion designer. Called the "Queen of the bias cut" and "the architect among dressmakers", Vionnet is best-known today for her elegant Grecian-style dresses and for introducing the bias-cut to the fashion world. 

Madeleine Vionnet 1939, by Christine, flickr