Counterparty risk is the potential for financial loss arising from a counterparty's inability or unwillingness to fulfill its contractual obligations in a transaction. As a core concept within financial risk management and market microstructure analysis, it investigates the assessment, measurement, and mitigation of default risk inherent in bilateral financial arrangements across various instruments (such as derivatives, bonds, and foreign exchange) and market structures. The study of counterparty risk is significant for understanding market stability, pricing complex financial products, and designing robust risk management frameworks, particularly in over-the-counter markets where central clearing mechanisms may be absent or less effective.