Despite earlier attempts to define global health, the discipline’s boundaries are unclear, its priorities defined more by funding high-income countries from the Global North than by global health trends. Governance and resource allocation are challenged by movements such as decolonizing global health. Inherent contradictions within global health derive from its historical evolution from tropical medicine and international health, as well as recent trends in infectious diseases. Demographic, socioeconomic, and epidemiologic transitions, including the rise in noncommunicable diseases, have eroded the concept of a binary world of developed and developing countries. Competitive tension has emerged between aspirations for global health security and health equity. Dominant principles should focus on vulnerable populations, transnational challenges such as migration and climate change, appropriate prevention and care, and epidemic preparedness and response capacity. As the 2030 target date for the United Nations Sustainable Development Goals approaches, reconceptualization of global health is required, or the discipline risks losing identity and relevance.