Risk data aggregation enables organizations to compile comprehensive risk exposures from disparate sources, systems, and legal entities into consistent, accurate enterprise-wide reporting. Effective aggregation requires data governance, common taxonomies, automated workflows, and robust reconciliation processes to ensure completeness and accuracy. The Basel Committee's BCBS 239 principles mandate strong risk data aggregation capabilities for global systemically important banks. Challenges include legacy systems, manual processes, and inconsistent definitions across business lines. During the 2008 financial crisis, many institutions discovered they could not aggregate exposures to counterparties like Lehman Brothers across trading desks and geographies quickly enough to manage risk effectively, leading to enhanced regulatory requirements for risk data infrastructure and aggregation capabilities.