Despite the vast literature available on the subject of “informality,” little attention has been paid to the mobilization of morphology as a regulatory device. This article explores the role of formalist ideologies in the production of exclusive spatial imaginaries through the notion of “morphological fetishism.” Planning discourse has often deployed this mechanism to stigmatize subaltern populations and to forge an archetypal idea of informality associated with poverty. The paper provides a brief synthesis of the literature on informality and some of its gaps, elaborates the concept of morphological fetishism to study the logics that demarcate the informal as the “other” of hegemonic socio-spatial orders, and explores different historical and geographical expressions of this process, showing its continuity over time.