Marie-Louise Jacotin was the daughter of a lawyer for a French bank, and the grand-daughter (through her mother) of a glassblower from a family of Greek origin.

On her second attempt, she placed second in the entrance examination for the École Normale Supérieure in 1926 (tied with Claude Chevalley), but by a ministerial decree was moved down to 21st position.

She returned to Paris in 1930, married another mathematician, Paul Dubreil, and joined him on another tour of the mathematics centers of Germany and Italy, including a visit with Levi-Civita.

[1][2][3] While her husband taught at Lille, Dubreil-Jacotin continued her research, finishing a doctorate in 1934 concerning the existence of infinitely many different waves in ideal liquids, under the supervision of Henri Villat.

[1] Following her husband, she moved to Nancy, but was unable to obtain a faculty position there herself because that was viewed as nepotism; instead, she became a research assistant at the University of Rennes.