Merck & Co., Inc. issued $6 billion in aggregate principal amount of debt securities on May 22, 2026. The offering consists of seven tranches: $500M Floating Rate Notes (2028), $1B 4.300% Notes (2028), $500M 4.650% Notes (2031), $1B 4.950% Notes (2033), $1.5B 5.200% Notes (2036), $500M 5.750% Notes (2046), and $1B 5.850% Notes (2056). The notes were issued under an existing indenture dated January 6, 2010, with U.S. Bank Trust National Association acting as trustee. The issuance was authorized by the Board of Directors via resolutions dated March 14, 2024, and November 18, 2025.