Marine spatial planning (MSP) seeks to integrate traditionally disconnected oceans activities, management arrangements, and practices through a rational and comprehensive governance system. This article explores the emerging critical literature on MSP, focusing on key elements of MSP engaged by scholars: (1) planning discourse and narrative; (2) ocean economies and equity; (3) online ocean data and new digital ontologies; and (4) new and broad networks of ocean actors. The implications of these elements are then illustrated through a discussion of MSP in the United States. Critical scholars are beginning to go beyond applied or operational critiques of MSP projects to engage the underlying assumptions, practices, and relationships involved in planning. Interrogating MSP with interdisciplinary ideas drawn from critical social science disciplines, such as emerging applications of relational theory at sea, can provide insights into how MSP and other megaprojects both close and open new opportunities for social and environmental well-being.