The Patient Protection and Affordable Care Act (PPACA), commonly called the Affordable Care Act (ACA) and nicknamed Obamacare, is a United States federal statute enacted by President Barack Obama on March 23, 2010.

Together with the Health Care and Education Reconciliation Act amendment, it represents the most significant regulatory overhaul of the U.S. healthcare system since the passage of Medicare and Medicaid in 1965. Under the act, hospitals and primary physicians would transform their practices financially, technologically, and clinically to drive better health outcomes, lower costs, and improve their methods of distribution and accessibility.

States were required to expand Medicaid eligibility to include individuals and families with incomes up to 133% of the federal poverty level.

The Affordable Care Act was designed to increase health insurance quality and affordability, lower the uninsured rate by expanding insurance coverage and reduce the costs of healthcare. It introduced mechanisms including mandates, subsidies and insurance exchanges. The law requires insurers to accept all applicants, cover a specific list of conditions and charge the same rates regardless of pre-existing conditions or sex.

The law and its implementation faced challenges in Congress and federal courts, and from some state governments, conservative advocacy groups, labor unions, and small business organizations. The United States Supreme Court upheld the constitutionality of the ACA’s individual mandate as an exercise of Congress’s taxing power, found that states cannot be forced to participate in the ACA’s Medicaid expansion, and found that the law’s subsidies to help individuals pay for health insurance are available in all states, not just in those that have set up state exchanges.

The ACA has caused a significant reduction in the number and percentage of people without health insurance, with 24 million covered during 2016. Increases in overall healthcare spending have slowed since the law was implemented, including premiums for employer-based insurance plans. The Congressional Budget Office reported in several studies that the ACA would reduce the budget deficit, and that repealing it would increase the deficit.