The St. Gall Priscian Glosses (Codex Sangallensis 904), abbreviated Sg., is an Irish manuscript of the Latin grammar Institutiones grammaticae by Priscian, held by the Abbey Library of St. Gall. It contains 9412 glosses, including 3478 in Old Irish.[1] Together with the Würzburg glosses on the Epistles of St Paul and the Milan glosses on a Commentary on the Psalms they provide the main source of Old Irish writing available today and thus serve as an important reference for linguistic research on Old Irish.[2]