The use of Information Technology (IT) without the approval and support of the IT department, called shadow IT, has challenged organizations to rethink ways to manage IT resources to cope with the use of unauthorized technologies within organizations. We review the literature on shadow IT to shed light on this phenomenon, discussing the conceptual definition and types, the related concepts, and its consequences. This study, then, is an effort to better understand the phenomenon based on the extant literature. We provide contributions by enhancing the emerging body of knowledge on shadow IT, as well as by suggesting research gaps to be addressed in future research in order to advance on the topic.