Ambrosiaster, the name given to the author of a commentary on St. Paul’s letters in the New Testament, long attributed to St. Ambrose (died 397), bishop of Milan. The work is valuable for the criticism of the Latin text of the New Testament.
In 1527 Erasmus expressed doubts that the work was written by Ambrose. His judgment was eventually accepted by scholars, and the author is generally called Ambrosiaster or Pseudo-Ambrosius. Since Augustine in the 4th century attributed some parts of the commentary on Romans to Sanctus Hilarius, the work has been ascribed by various scholars to almost every known Hilary.