This volume is a compendium of all known commentaries on Hebrew liturgical poetry (piyyut) preserved in manuscript form. It includes references to commentaries from many different Jewish communities, most prominent among them Ashkenaz, Tsarfat, Sepharad, Carpentras and Yemen, composed and copied in Medieval and Early Modern times. Over 18,000 individual commentaries on more than 2,000 poems are listed with primary sources and references to editions where extant. As an aid to research, it describes a vast but hitherto neglected genre of medieval Hebrew literature and maps out a whole new field of investigation into medieval Jewish textual culture. This catalogue enables users to find manuscript commentaries on most piyyutim that were included in liturgies in major Jewish communities.