Neural stem cells (NSCs) are progenitor cell populations generating glial cells and neurons and endowed with long-lasting self-renewal and differentiation potential. While some neural progenitors (NPs) in the embryonic nervous system are also long-lived and match this definition, the term NSC classically refers to such progenitor types in the adult. With the discovery of extensive NSC populations in the adult brain of Danio rerio (zebrafish) and of their high neurogenic activity, including for neuronal regeneration, this model organism has become a powerful tool to characterize and mechanistically dissect NSC properties. On these bases, this article will consider NSCs in the adult zebrafish brain, with a focus on its most extensively characterized domain, the telencephalon (notably its dorsal part, the pallium). Whenever necessary, we will also refer to other brain subdivisions, embryonic processes, and the mouse adult brain, whether for comparative purposes or because more information is available in these other systems.