Background: Lebanon is undergoing substantial demographic and social change, with older adults comprising approximately 10% of the population. The Late Life Learning, Cognition, and Aging (3LC) study was established around the University for Seniors (UfS), a longstanding late-life learning program at the American University of Beirut. The cohort was designed to leverage variation in late-life learning exposure by including both UfS participants and community-dwelling adults without prior participation in the program. This provides a unique opportunity to investigate how late-life learning, lifecourse social and biological factors, and health behaviors relate to cognitive aging, dementia risk, mental health, and resilience in Lebanon. Methods: Participants aged 50 years and older are recruited from the UfS program and the surrounding community in Lebanon. Baseline assessments include an interviewer-administered questionnaire, standardized anthropometric and sensory assessments, and blood collection for biomarker measurement and biobanking. The questionnaire captures health, psychosocial, cognitive, social engagement, and lifecourse factors, including exposure to war, conflict, and socioeconomic adversity. Longitudinal follow-up includes planned phone-based and in-person assessments at approximately two-year intervals. Results: The cohort comprised 1,871 participants, including 536 UfS participants (350 previously enrolled and 186 newly enrolled) and 1,335 community participants, of whom 1,041 were age-, sex-, and education-matched to UfS participants and 294 were additionally recruited without matching. The mean age was 65.6 years (SD=9.0), and 70.1% of participants were women. Blood samples were obtained from 1,541 participants (82.3%). Conclusion: The 3LC study provides a unique platform to examine how late-life learning and lifecourse factors shape cognitive aging, well-being, and dementia risk in Lebanon. By integrating social, psychosocial, health, and biological measures, the cohort offers opportunities to identify modifiable determinants of cognitive aging and inform dementia prevention in Lebanon and other under-resourced settings.