This extensive document explores the Big Debt Cycle, a long-term financial phenomenon characterized by periods of credit expansion culminating in unsustainable debt burdens and subsequent deleveraging. The author, a global macro investor, argues this cycle, typically lasting around 80 years, is not widely understood but is critical for investors and policymakers. The text outlines five stages of this cycle, from the initial "sound money" phase to the eventual "deleveraging" where debt is reduced through defaults, restructurings, or money printing. Mathematical formulas are presented to demonstrate how debt burdens compound and how different factors, such as interest rates, income growth, and deficits, influence debt sustainability. Ultimately, the author contends that central banks inevitably choose to print money and devalue the currency to alleviate debt crises, and that this cycle interacts with other major global forces like political and geopolitical dynamics, acts of nature, and technological advancements.