This entry introduces Karen Barad, Professor of History of Consciousness at the University of California at Santa Cruz, California, USA. From their background in theoretical physics and feminist theory, Barad developed the framework of agential realism, a philosophy of science perspective grounded in a specific ethico-epistem-ontology. This framework reconceptualizes the relationship between matter, discourse, and agency by rejecting dualisms and emphasizing that reality is enacted through material-discursive intra-actions. The hyphenation of ethico-epistem-ontology signals Barad’s core claim that ontology, epistemology, and ethics are inseparably entangled. To apply the agential realist philosophy of science perspective in psychology has several implications for topics that are also discussed in theoretical and philosophical psychology, such as the conceptualization of objects, respectively, psychological concepts of objects, the conceptualization of the researcher’s position within research, and the conceptualization of the research process as a way to gain knowledge. Agential realism understands psychological constructs like emotion, cognition, or behavior as entities-within-phenomena, enacted through material-discursive practices. This shifts the focus from discovering inherent qualities to investigating how specific configurations give rise to contingent and local manifestations. Furthermore, Barad’s framework emphasizes that researchers are part of the very phenomena they study. Researchers co-create what becomes knowable and are therefore ethically responsible not just for knowledge production but also “for what exists.” Finally, Barad’s agential realism views research as a practice that enacts agential cuts—separating certain possibilities from others. While Barad has not yet been widely cited in psychology, they provide elaborate contributions to philosophy of science questions for psychology.