The 2007-2008 financial crisis was a "run on repo," a liquidity crisis in the repo market, which is a major short-term market providing financing for securitization and financial institutions. The crisis was driven by the collapse of securitized banking, which involves packaging and reselling loans, primarily through repo agreements. The paper argues that securitized banking was central to the crisis, as it involved the sale and repurchase of securitized bonds, which became collateral for repo transactions. The crisis spread from subprime housing assets to non-subprime assets, with the LIB-OIS spread, a proxy for counterparty risk, strongly correlated with changes in credit spreads and repo rates for securitized bonds. This correlation indicated higher uncertainty about bank solvency and lower values for repo collateral. Concerns about the liquidity of markets for the bonds used as collateral led to increases in repo "haircuts," the amount of collateral required for any given transaction. With declining asset values and increasing haircuts, the U.S. banking system became effectively insolvent for the first time since the Great Depression. The paper uses a novel dataset of 392 securitized bonds and related assets to trace the crisis. It shows that the crisis spread from subprime housing assets to non-subprime assets, with the LIB-OIS spread being a key indicator of counterparty risk. The paper also discusses the differences between traditional banking and securitized banking, highlighting the role of repo markets in securitized banking. The crisis was characterized by a "run on repo," where the demand for collateral increased, leading to higher haircuts and a liquidity crisis. The paper provides empirical evidence of this run on repo, showing that the LIB-OIS spread and the ABX index were key indicators of the crisis. The crisis was global, affecting non-U.S. markets as well. The paper concludes that the crisis was a systemic event, with the banking system becoming insolvent due to the collapse of securitized banking and the run on repo.The 2007-2008 financial crisis was a "run on repo," a liquidity crisis in the repo market, which is a major short-term market providing financing for securitization and financial institutions. The crisis was driven by the collapse of securitized banking, which involves packaging and reselling loans, primarily through repo agreements. The paper argues that securitized banking was central to the crisis, as it involved the sale and repurchase of securitized bonds, which became collateral for repo transactions. The crisis spread from subprime housing assets to non-subprime assets, with the LIB-OIS spread, a proxy for counterparty risk, strongly correlated with changes in credit spreads and repo rates for securitized bonds. This correlation indicated higher uncertainty about bank solvency and lower values for repo collateral. Concerns about the liquidity of markets for the bonds used as collateral led to increases in repo "haircuts," the amount of collateral required for any given transaction. With declining asset values and increasing haircuts, the U.S. banking system became effectively insolvent for the first time since the Great Depression. The paper uses a novel dataset of 392 securitized bonds and related assets to trace the crisis. It shows that the crisis spread from subprime housing assets to non-subprime assets, with the LIB-OIS spread being a key indicator of counterparty risk. The paper also discusses the differences between traditional banking and securitized banking, highlighting the role of repo markets in securitized banking. The crisis was characterized by a "run on repo," where the demand for collateral increased, leading to higher haircuts and a liquidity crisis. The paper provides empirical evidence of this run on repo, showing that the LIB-OIS spread and the ABX index were key indicators of the crisis. The crisis was global, affecting non-U.S. markets as well. The paper concludes that the crisis was a systemic event, with the banking system becoming insolvent due to the collapse of securitized banking and the run on repo.