This chapter discusses the epidemiology of type 1 diabetes (T1D) globally and across the lifespan. It highlights the increasing incidence of T1D, which has risen by 2–5% worldwide, with a prevalence of approximately 1 in 300 in the US by age 18. The disease is influenced by genetic and environmental factors, with a complex interplay between them. T1D is characterized by the autoimmune destruction of pancreatic beta cells, leading to insulin deficiency. It accounts for 5–10% of all diabetes cases worldwide, while type 2 diabetes (T2D) is more prevalent in adults. The chapter reviews the incidence and prevalence of T1D, risk factors such as age, gender, race/ethnicity, and genotype, and the clinical course of the disease. It also discusses treatment and management strategies, complications, and the importance of epidemiologic studies in understanding and addressing T1D. The chapter emphasizes the need for further research to improve care and find a cure for T1D.This chapter discusses the epidemiology of type 1 diabetes (T1D) globally and across the lifespan. It highlights the increasing incidence of T1D, which has risen by 2–5% worldwide, with a prevalence of approximately 1 in 300 in the US by age 18. The disease is influenced by genetic and environmental factors, with a complex interplay between them. T1D is characterized by the autoimmune destruction of pancreatic beta cells, leading to insulin deficiency. It accounts for 5–10% of all diabetes cases worldwide, while type 2 diabetes (T2D) is more prevalent in adults. The chapter reviews the incidence and prevalence of T1D, risk factors such as age, gender, race/ethnicity, and genotype, and the clinical course of the disease. It also discusses treatment and management strategies, complications, and the importance of epidemiologic studies in understanding and addressing T1D. The chapter emphasizes the need for further research to improve care and find a cure for T1D.