This paper investigates how the members of the Kigye Yu lineage imagined and invented their ancestral roots during the Chosŏn dynasty (1392–1910) and how such a pursuit of ancestral origins led to subsequent developments in genealogical records. As early as the fifteenth century, Chosŏn elites began to show interests in genealogy that included identifying remote ancestors from ancient times for various political, social, and cultural reasons. From the seventeenth century, the transformation of kinship organization in line with the Confucian ideal of patriliny and elites’ competition for power and prestige intensified genealogical consciousness. Elites became heavily invested in searching for ancestral origins in the form of their lineages’ founders and their tombs. While claiming to rely on documentary and physical evidence, elites often deviated from their professed empiricism and adopted evidence from dubious sources such as oral testimonies and geomancy to rationalize invented ancestral roots. Such pliable approaches, often observed in other early modern cultures such as late imperial China and Europe, opened a floodgate of lineages glorifying their ancestry by pushing their origins back even to mythical founders of ancient Korean and Chinese kingdoms, and adorning their lineages with invented heroes. At the same time, loopholes and blank spots in genealogies enabled quasi- and nonelites to become a member of prominent lineages by grafting their names onto their family trees.