Guatemala is home to a rich cultural heritage of music. Composers whose works are present in the Archivo Historico Arquidiocesano de Guatemala (AHAG) include, Tomás Luis de Victoria, Philippe Verdelot, Baldassare Galuppi, Adolf Hasse, Giovanni Battista Pergolesi, and Ignacio Jerusalem. Among this repertoire is the Mass for Eight Voices in D major by José de Nebra (1702-1768), which until now has been un-known to researchers. The manuscript of the Mass for Eight Voices in Guatemala City is the only known extant copy and provides a glimpse into the musical life of the Cathedral of Santiago de Los Caballeros in the eighteenth century. This dissertation is a transcription of Nebra’s mass and also includes a catalogue of extant pieces written by Nebra that are held at the AHAG. A discussion of Nebra and the chapelmasters who performed his music in Guatemala is presented. The final product is a critical edition of the Mass for Eight Voices making performances of this work possible by modern ensembles.