The Cartulary of the Lembos monastery near Smyrna, preserved in Vind. hist. gr. 125, is one of the richest and historically most important collections of legal documents that has come down to us from the Byzantine world. After its restoration by Emperor John III Vatatzes, the Lembos monastery quickly developed into one of the leading imperial foundations in Byzantine Asia Minor during the Nicaean Empire and the early Palaiologan period. The 207 pieces preserved in the monastery’s cartulary were, for the greatest part, issued in the years 1224–1294 by a broad range of public authorities, such as the imperial court, state officials, various law courts, the metropolis of Smyrna, and local notaries. The collection constitutes a prime source for secular and ecclesiastical institutions, fiscal administration, land use, rural economy, topography, and prosopography of Byzantine Asia Minor and thirteenth-century Byzantium. This is the first complete critical and annotated edition of the cartulary with detailed English summaries and replaces the partial edition of F. Miklosich and J. Müller in the Acta et Diplomata graeca medii aevi series of 1871.