Retirement decumulation is the systematic process by which individuals convert accumulated retirement assets into sustainable income streams or expenditures throughout their post-employment years. As an academic concept and research field, it investigates the complex financial, behavioral, and economic challenges associated with managing wealth during the period of drawing down savings, contrasting sharply with the wealth accumulation phase. It examines optimal spending strategies, asset allocation during drawdown, income sequencing, the role of guaranteed income sources, longevity risk, inflation risk, tax implications, and psychological factors influencing spending behavior. Its significance lies in addressing the critical need for individuals to maintain financial security and well-being throughout retirement, informing policy design, financial planning practices, and individual decision-making to prevent premature depletion of assets and ensure adequate lifetime income.