The Centers for Medicare and Medicaid Services (CMS) is a federal agency within the U.S. Department of Health and Human Services (HHS) that administers the Medicare and Medicaid programs.

Medicare is a federal health insurance program for people who are 65 or older, certain younger people with disabilities, and people with End-Stage Renal Disease (permanent kidney failure requiring dialysis or a transplant, sometimes called ESRD). Medicaid is a joint federal and state program that provides health coverage to low-income individuals and families.

CMS is responsible for overseeing the administration of these programs, including setting policies and rules, paying claims, and monitoring the quality and effectiveness of care provided to beneficiaries. CMS also works to improve the efficiency and effectiveness of the healthcare system, and to promote public health through initiatives such as the promotion of electronic health records and the implementation of value-based payment models.

In addition to administering Medicare and Medicaid, CMS also oversees other programs such as the Children's Health Insurance Program (CHIP) and the Health Insurance Marketplace, which helps individuals and families find affordable health insurance coverage. CMS also plays a role in addressing the opioid epidemic through initiatives such as the Opioid Misuse Prevention measure in the Quality Payment Program.