This article uses a simple life-cycle economic model of retirement to characterize the optimal retirement age and the effects of the wage rate, wealth, and the time horizon on that age. The model is then extended to include pensions, both public and private, which can produce non-convexities in the lifetime budget constraint. The model is further extended to include health effects on retirement, uncertainty and joint retirement (the coordination of retirement dates by husband and wife). The chapter concludes with a discussion of retirement in the context of behavioural economics.