Research on the origins of the violoncello reveals considerable dispute concerning the existence and identity of its ancestor, the bass violin. This study focuses on the classification of the sixteenth- and early seventeenth-century bass violin by means of the following criteria: construction, early history and development, role due the social status of builders and players, use within the violin band, performing positions, and defining terminology. Accounts of inventories, organological treatises, music theoretical writings, lists of households and royal courts, descriptions of feasts, reports of choreographies and iconographical examples confirm the bass violin's presence in the late sixteenth century and beyond. Three of the earliest unchanged extant organological examples embody, complement and corroborate the bass violin's identification, and conclude the essay.