This article, part of a symposium on comparative financial regulation, compares the United States's and European Union's approaches to systemic risk and macroprudential regulation since the 2008 global financial crisis. It reveals that both jurisdictions have established new macroprudential bodies and given regulators new macroprudential tools, including macroprudential buffer requirements and borrower-based macroprudential measures. However, significant differences exist in how the U.S. and EU have implemented macroprudential regulation, reflecting their distinct regulatory traditions, institutional structures, and political constraints. These differences have important implications for the effectiveness of systemic risk regulation and suggest potential avenues for mutual learning.