Ambrosiaster ("Star of Ambrose") is the name given to the anonymous author of the earliest complete Latin commentary on the thirteen epistles of Paul. The commentaries were thought to have been written by Ambrose throughout the Middle Ages, but their authorship was challenged by Erasmus, whose arguments have proved decisive.

The commentaries, which serve as important witnesses to pre-Vulgate Latin versions of Paul's epistles, are noteworthy in several respects. Ambrosiaster was a careful and thoughtful interpreter, who made little use of allegory, though he employed typology judiciously. Writing during the pontificate of Damasus (366-384), he is a witness to Nicene orthodoxy and frequently comments on themes related to the Trinity, the consubstantiality of the Son, the problem of the unbelief of the Jews and the nature of human sinfulness. He had a keen eye for moral issues and often offers comments that reflect his knowledge of how the church had changed from the time of the apostles to his own day.

Here for the first time his commentaries on Galatians, Ephesians, Philippians, Colossians, 1-2 Thessalonians, 1-2 Timothy, Titus and Philemon are made available in English, ably translated and edited by Gerald L. Bray.