Beginning in the late Middle Ages and continuing into the early modern period, merchants throughout western Europe became influential members of the growing middle class, and with this growing wealth and influence also came artistic patronage. Although the patronage of merchants from other areas of the western world, specifically Italy and Northern Europe, has been studied in some detail, the examination of merchant patrons from Iberia, and specifically Castile, has been largely neglected. Accordingly, this study offers unprecedented analysis of the funerary altarpiece commissioned at the turn of the sixteenth century by the Castilian merchant Gonzalo Lopez de Polanco for the high altar of the parish church of San Nicolas de Bari in Burgos, Spain. Through the analysis of this altarpiece, this project examines the devotional life and social aspirations of the merchant patron as well as the function of the altarpiece in its original location, doing so through the consideration of contemporary liturgical and devotional texts as well as the patron's testament. Moreover, this study addresses how this altarpiece compares to others commissioned by merchant, noble, ecclesiastical and royal patrons in Burgos around the turn of the sixteenth century, a time when Castilian attitudes toward religious devotion were changing due to increased contact with the rest of Europe and the importation of various religious texts under Ferdinand and Isabel. By centering this project on an object commissioned by a member of the merchant class, analysis of this altarpiece offers an initial study of the religious life and artistic patronage of early sixteenthcentury Castilian merchants.