Universities of the Third Age (U3A), lifelong learning institutes, and "senior universities" are terms used to describe organizations that provide education for older adults, specifically for those who are retired or in the "third age" of life. The purpose of this article is to provide a comprehensive, historical overview of the evolution of these organizations across global settings. This article highlights the importance of older adult education while discussing U3A's structure and models. The article explores the origins and historical development of the U3A model and its influence on recent initiatives like the Age-Friendly Universities movement. It then focuses on the impact of French and British Models of U3A on providing older adult education. There is a general discussion of the expansion of these organizations in several countries and a comparison of each's curricular structure and approach. The article concludes with suggested future directions and potential areas of improvement (e.g. technology access, accessibility, and inclusion of older adult learners; diverse needs and interests) and ways these models can remain relevant to the ever-changing older adult learner population. Through this analysis, the article contributes to the understanding of U3A organizations and their role in promoting lifelong learning for older adults.