This paper reviews several streams of research on market category formation. Most past research has largely focused on established category systems and the antecedents and consequences of categorical positioning (i.e., categorical purity vs. spanning; combination vs. replacement) but relatively ignored the formative processes leading to new categories. In this review, we address this lacuna to posit that scholarship would benefit from clearly disentangling category emergence from category creation. We analytically describe the differences between the two and elaborate the boundary conditions that guide and define which process is more likely to occur in a given market. Our review contributes to illuminating the role of organizational agency and strategic actions in market categories and their formation, which deserve greater attention as a result of their theoretical and practical implications.