The internationalization of higher education has been driven by an increasingly globalized and interconnected world. One concept that embodies this internationalization process is global citizenship, which can be promoted through student mobility, internationalization-at-home, or other forms of intercultural learning. While global citizenship remains a broad and highly contested term, the increased interest of its role in higher education has inspired research in different fields. The aim of this paper is to provide a review of existing research approaches to studying global citizenship, and to formulate future research directions that may integrate these approaches into a holistic framework. By reviewing literature from different fields in the social sciences, we have identified three main research approaches: intercultural competence, social identification with a global community, and civic engagement. While each approach reflects an important dimension of global citizenship, they remain separate in the literature, complicating the understanding and application of global citizenship in higher education. Therefore, for each approach we present a general conceptualization and a brief overview of prior findings. We discuss how integrating these approaches can lead to a more holistic understanding of global citizenship and guide future avenues for research and practice in higher education.