This chapter provides an overview of the (de)institutionalization of retirement across welfare states, the main theoretical lenses in explaining policy mixes and retirement outcomes, and the recent changes in late-career patterns and rising social inequalities among older workers. Since the 1990s when early retirement was at its peak, pension and labour market reforms have been implemented to cut support for early retirement, leading to increases in older workers’ employment across OECD countries. Studies across the social sciences explain this turnaround from different perspectives, focusing on factors such as financial incentives to retire early, multilevel interactions between push, pull, and retention factors, cultures and norms of retirement, and linked life courses across individuals and over time. Recent research explores diversification in late careers and rising social inequalities among older workers. This chapter suggests that future research should take prior employment trajectories and partial retirement into account to understand diversified retirement outcomes.