Jacqueline Ferrand was born in 1918 in Alès in south-central France. An excellent student, she received the first prize in a national competition in mathematics as a student in the lycée in Nimes. Encouraged to take the entrance examination to the Paris École Normale Supérieure, in 1936 she was among the first group of girls admitted to this school, where she studied mathematics and science. In 1939 she ranked first in the agrégation masculine in mathematical sciences (a competitive examination for positions in the public education system) along with Roger Apéry. Francois Apéry recounts the following story by the great French mathematician Jean Dieudonné, who recalled: "I was a member of the agrégation jury, for the only time in my life, by the way, and I gave a rather unusual analysis problem. Only two of the papers impressed me with their sense of analysis and precocious maturity very rare among candidates for the agrégation. Those two were Roger Apéry and Jacqueline Ferrand."
Ferrand immediately began teaching mathematics at the École Normale Supérieure de Jeunes Filles (a school for girls) and preparing the students for the agrégation. She also began mathematical research under the supervision of Arnaud Denjoy. Her first three papers on conformal representation were published in 1941. In June 1942 she defended her thesis for the Doctorat-ès-Sciences, published in two parts as "Étude de la correspondence entre les frontières dans la représentation conforme" and "Étude de la représentation conforme au voisinage de la frontière." Her thesis research won the Prix Girbal-Baral from the Académie des Sciences in 1943. In 1943 Ferrand became an assistant professor at the University of Bordeaux, then moved to the University of Caen in 1945. In 1947 Ferrand married Monsieur Lelong. From 1948 to 1956 she held the chair of calculus and higher geometry at the University of Lille. After spending a sabbatical at Princeton University, she became a full professor at the University of Paris where she remained until her retirement in 1984. She was one of the first female full professors on the science faculty at Paris.
Ferrand's main research area was analysis and geometry. MathSciNet lists almost 100 publications (under Lelong-Ferrand and Ferrand), the last appearing in 1999. She is the author of 10 books. A four-volume textbook for an undergraduate course of study in mathematics was written with Jean-Marie Arnaudiès during the early 1970's for students at the University of Paris. Her last book, published in 1985, is devoted to the foundation of geometry and was developed for prospective teachers. In 1970 Edna Kramer wrote about Ferrand:
"Her major specialties have been conformal representation (1942-1947), potential theory (1947-1954), Riemann manifolds and harmonic forms (1955-present). Her 1942 thesis...and several subsequent papers investigated the behavior of conformal transformations in the neighborhood of a boundary point. Among her next set of memoirs was one where she created the concept of preholomorphic functions, using these to produce a new methodology for proofs. Her research in potential theory enabled her to generalize certain classic theorems to n dimensions, namely the lemmas of Julia and Phragmen-Lindeloef. Following this work, she attacked some of the most difficulty problems in the field, once again creating new concepts for this purpose. She dropped this avenue of research temporarily to write a searching, comprehensive treatise, which was published in 1955 as part of the Collections de Cahiers Scientifiques edited by Professor Gaston Julia and entitled Représentation conforme et transformations à intégrale de Dirichlet bornée. Then, having explored the field of conformal representations so completely, she felt that it was time to enlarge the scope of her research, an objective realized in the many original papers which she contributes year after year. There have been new books too—a work on the fundamental concepts of mathematics with emphasis on analysis, and an advanced text on differential geometry.