IntroductionDebate around a common definition of global health has seen extensive scholarly interest within the last two decades; however, consensus around a precise definition remains elusive. The objective of this study was to systematically review definitions of global health in the literature and offer grounded theoretical insights into what might be seen as relevant for establishing a common definition of global health.MethodA systematic review was conducted with qualitative synthesis of findings using peer-reviewed literature from key databases. Publications were identified by the keywords of ‘global health’ and ‘define’ or ‘definition’ or ‘defining’. Coding methods were used for qualitative analysis to identify recurring themes in definitions of global health published between 2009 and 2019.ResultsThe search resulted in 1363 publications, of which 78 were included. Qualitative analysis of the data generated four theoretical categories and associated subthemes delineating key aspects of global health. These included: (1) global health is a multiplex approach to worldwide health improvement taught and pursued at research institutions; (2) global health is an ethically oriented initiative that is guided by justice principles; (3) global health is a mode of governance that yields influence through problem identification, political decision-making, as well as the allocation and exchange of resources across borders and (4) global health is a vague yet versatile concept with multiple meanings, historical antecedents and an emergent future.ConclusionExtant definitions of global health can be categorised thematically to designate areas of importance for stakeholders and to organise future debates on its definition. Future contributions to this debate may consider shifting from questioning the abstract ‘what’ of global health towards more pragmatic and reflexive questions about ‘who’ defines global health and towards what ends.