In this chapter provides a comprehensive overview of Long COVID and its most prevalent manifestation, fatigue, tracing the evolution of our understanding from the emergence of COVID-19 in December 2019 through 2024. First, the chapter examines the societal and economic impact of long COVID, affecting an estimated 400 million individuals globally by 2023, with annual economic costs reaching approximately $1 trillion. Through careful analysis of major research milestones and epidemiological studies, the text explores the condition’s prevalence, with fatigue affecting approximately 75% of Long COVID patients. The chapter presents detailed visualizations illustrating the chronological development of COVID-19 and Long COVID research, global cumulative incidence, economic impact across major Western economies, and the distribution of major symptoms. Special attention is given to the complex socioeconomic implications of the condition, including its disproportionate impact on marginalized communities and women and its threat to sustainable development goals. The chapter also examines workforce participation effects, with studies showing affected individuals being 10% less likely to be employed and working 25–50% fewer hours when employed. The text concludes by emphasizing the urgent need for continued research into underlying mechanisms and effective treatment strategies, setting the foundation for the book’s exploration of this significant public health challenge.