Ever since the Greek philosophers and fabulists pondered the question “What is man?,” inquiries into the concept of the subject have troubled humanists, eventuating in fierce debates and weighty tomes. In the wake of the Descartes’s cogito and Enlightenment thought, proposals for an ontology of the idealist subject’s rationality, autonomy, and individualism generated tenacious questions regarding the condition of pre-consciousness, the operation of feelings and intuitions, the subject-object relation, and the origin of moral and ethical principles. Throughout the 19th and 20th centuries, Marx, and theorists he and Engels influenced, pursued the materialist bases of the subject, through analyses of economic determinism, self-alienation, and false consciousness. Through another lineage, Freud and theorists of psychic structures pursued explanations of the incoherence of a split subject, its multipartite psychodynamics, and its relationship to signifying systems. By the latter 20th century, theorizations of becoming a gendered woman by Beauvoir, of disciplining power and ideological interpellation by Foucault and Althusser, and of structuralist dynamics of the symbolic realm expounded by Lacan, energized a succession of poststructuralist, postmodern, feminist, queer, and new materialist theorists to advance one critique after another of the inherited concept of the liberal subject as individualist, disembodied (Western) Man. In doing so, they elaborated conditions through which subjects are gendered and racialized and offered explanatory frameworks for understanding subjectivity as an effect of positionality within larger formations of patriarchy, slavery, conquest, colonialism, and global neoliberalism. By the early decades of the 21st century, posthumanist theorists dislodged the subject as the center of agentic action and distributed its processual unfolding across trans-species companionship, trans-corporeality, algorithmic networks, and conjunctions of forcefields. Persistently, theorists of the subject referred to an entangled set of related but distinct terms, such as the human, person, self, ego, interiority, and personal identity. And across diverse humanities disciplines, they struggled to define and refine constitutive features of subject formation, most prominently relationality, agency, identity, and embodiment.