This paper examines the issue of what the self is by reviewing neuropsychological research, which converges on the idea that the self may be more complex and differentiated than previous treatments of the topic have suggested. Although some aspects of self-knowledge such as episodic recollection may be compromised in individuals, other aspects—for instance, semantic trait summaries—appear largely intact. Taken together, these findings support the idea that the self is not a single, unified entity. Rather, it is a set of interrelated, functionally independent systems. Implications for understanding the self in various areas of psychological research—e.g., neuroimaging, autism, amnesia, Alzheimer's disease, and mirror self-recognition—are discussed in brief.