Gregor Zallwein (20 October 1712, Oberviechtach, Oberpfalz - 6 or 9 August 1766, Salzburg) was an Austrian expert on canon law.
Upon the request of the Prince-bishop of Gurk, Joseph Maria Count of Thun, he was sent as professor of canon law to the newly erected seminary at Salzburg in Carinthia.
From 1749 until his death he was professor of canon law at the Benedictine University of Salzburg, where he held at the same time the office of "Rector magnificus" from 1759.
Unlike most German canonists of his time, he laid great stress on the sources and historical development of canon law.
Though his juristic writings are at times not clear, his lectures were highly valued and attended by students from foreign countries.