This scoping review presents the extent and nature of the body of literature on illicit online pharmacies (IOPs) and identifies research gaps. Using the five-step framework developed by Arksey and O’Malley, we searched PubMed, Web of Science, EMBASE, CINAHL, Science Direct and PsycInfo to retrieve relevant studies published in English in peer-reviewed journals. The search strategy identified forty-three articles that met the inclusion criteria. Ten themes were identified and categorized into five clusters: patient risk, healthcare providers, marketing and supply chain, public health and society, and policy and regulation. Research into these clusters has evolved over time and has focused increasingly on issues related to specific drugs rather than the overall phenomenon. Data collection has been dominated by convenience sampling, online searches, content analysis and surveys. Data analysis remains primarily descriptive. Gaps within the extant literature suggest an agenda for future research into regulation and enforcement; public health awareness and education; healthcare services; risks to patients and public health; patient-, price- and product-related issues; website design; social media promotion; and supply chains and logistics. We conclude that IOPs are vastly understudied and suggest an urgent need for further empirical and conclusive research.