Jean de La Fontaine, de Fonte, clerk of the diocese of Bayeux described in 1403 as master of arts and student in law, was bachelor and promoter of the University in 1421, and was sent to Bedford and Henry VI in 1422 to obtain confirmation of the privileges of the University; he was licentiate in law at Paris in 1424.

In 1427, with Guillaume Colles, Manchon and Robert Guérould, he edited the transaction, made with great care by Pierre Cauchon, between the Archbishop and the Chapter of Rouen. Jean de La Fontaine read, in 1436, Charles VII's confirmation of the privileges of the University.

Commissioned assistant counselor of the Trial, delegated by Pierre Cauchon to question Jeanne, La Fontaine advised her to submit to the Church. Upon the testimony of Manchon and Massieu, which need not be taken too literally, he had to flee Rouen under the threats of Cauchon, who found him too favorable to the accused.

We do know also that he was a friend of Nicolas de Houppeville, to whom he passed a letter while the latter was in prison. A Guillaume de La Fontaine was cited as lieutenant-general of Jean Salvain, Bailly of Rouen in 1432. A Jacques de La Fontaine, bachelor of law, secretary and intimate friend of the Pope, was, on March 27, 1429, occupied in the matter of exchanging his canonicate of Beauvais.