Ambrosiaster or Pseudo-Ambrose is the name given to the unknown author of a commentary on the epistles of Saint Paul, written some time between 366 and 384 AD.
Pseudo-Ambrose was the name given by Erasmus to refer to the author of a volume containing the first complete Latin commentary on the Pauline epistles.
This is extremely problematic, though, since it would require Ambrose to have written the book before he became a bishop, and then added to it in later years, incorporating later remarks of Hilary of Poitiers on Romans.
Internal evidence from the documents has been taken to suggest that the author was active in Rome during the period of Pope Damasus, and, almost certainly, a member of the clergy.
[6] In 1905, Alexander Souter established that Ambrosiaster was also the author of the Quaestiones Veteris et Novi Testamenti, a lengthy collection of exegetical and polemical tractates which manuscripts have traditionally ascribed to Augustine.