Remi-Casimir Oudin (14 February 1638 – September 1717) was a French Premonstratensian monk and bibliographer, who later in life was a Protestant convert, and a librarian in Leyden.

Finally, after taking charge for a while of the Church of Epinay-sous-Gamaches, in the diocese of Rouen, he retired into a convent in 1677 to resume his former scientific labors.

But his superiors, frightened at an intimacy which sprung up between him and the renowned Jurieu, confined him to the abbey of Ressons near Beauvais, in 1692.

The severe penances to which he was subjected contributed also to disgust him with monastic life; and having finally succeeded in escaping to Holland in 1692; he made an open profession of Protestantism at Leyden.

This work which is far from supplying all the authors omitted by Bellarmine, contains, according to Cave, a large number of errors: — Le Premontré défroqué (Leyden, 1692, 12mo): — Veterum aliquot Galliae et Belgii scriptorum opuscula sacra numquam edita (ibid.

In this work he claims that the Codex Alexandrinus dates only from the 10th century, and that the questions Ad Antiochum principem were attributed by mistake to St. Athanasius; — De scriptoribus Ecclesiae antiquis (Leips.