The Constitution of the United States is the supreme law of the United States of America, establishing the framework of the federal government, enumerating and limiting its powers, and codifying certain rights of the people and the states. Drafted in Philadelphia during the Constitutional Convention of 1787, it was ratified on 21 June 1788 when New Hampshire became the ninth state to approve it, satisfying the requirement of Article VII. It has been amended twenty-seven times; the first ten amendments, ratified on 15 December 1791, are collectively known as the Bill of Rights. The Constitution is among the oldest written national constitutions still in active operation.

The original Constitution consists of a Preamble and seven Articles. Article I establishes the bicameral Congress and its legislative powers; Article II establishes the executive branch and the presidency; Article III establishes the federal judiciary; Articles IV through VI address relations among states, the amendment process, federal supremacy, and oaths of office; Article VII specifies the ratification procedure. The document does not enumerate all powers of government but instead grants specific powers to the federal government, with the Tenth Amendment reserving remaining powers to the states or the people. The twenty-seven amendments address topics ranging from freedom of speech and religion (First Amendment) to the abolition of slavery (Thirteenth Amendment) to the direct election of senators (Seventeenth Amendment).

Federal courts, including the Supreme Court, have the authority to interpret the Constitution's meaning in cases and controversies - a power of judicial review established by practice and affirmed in Marbury v. Madison (1803), though not explicitly stated in the text. Interpretation is a subject of ongoing legal and academic debate. Originalists argue that the Constitution should be interpreted according to the text's original public meaning or the framers' intent at ratification. Living constitutionalists argue that its meaning should evolve with changing social conditions and values. Textualists focus narrowly on the words of the document independent of historical context or intended consequences. These schools of interpretation frequently yield different outcomes in contested cases and divide jurists, legal scholars, and the public. See Constitution of the United States - Debate.

The Constitution replaced the Articles of Confederation, which had governed the United States since 1781 but were widely regarded as inadequate for maintaining national cohesion and fiscal stability. The Convention of 1787 was called ostensibly to revise the Articles but produced an entirely new document. Ratification was contested, with Federalists and Anti-Federalists producing an extensive body of arguments - most notably the Federalist Papers - that continues to inform constitutional interpretation. The history of the Constitution, including its drafting, ratification, and subsequent amendment, is covered in Constitution of the United States - History.

There is broad legal and scholarly consensus that the Constitution is the supreme law of the land and that federal courts hold interpretive authority over constitutional questions. There is no comparable consensus on the correct method of constitutional interpretation; originalism, living constitutionalism, and textualism each command substantial academic and judicial support. See Constitution of the United States - Legal Consensus.

• Originalism - The Constitution should be interpreted according to its text's original public meaning or the specific intentions of its framers. Viewpoint: Originalism
• Living Constitutionalism - The Constitution's meaning is not fixed at ratification and should be interpreted to reflect contemporary values and circumstances. Viewpoint: Living Constitutionalism
• Textualism - The Constitution should be interpreted according to the plain meaning of its text, independent of historical context, framers' intent, or intended consequences. Viewpoint: Textualism
• Federal Supremacy - The federal government's constitutional authority supersedes state law in areas of conflict, and broad federal power is consistent with the constitutional design. Viewpoint: Federal Supremacy
• States' Rights - The Ninth and Tenth Amendments reserve substantial authority to states and the people, and federal power has expanded well beyond its constitutional limits. Viewpoint: States' Rights
• Individual Rights Primacy - The Constitution's primary purpose is the protection of individual rights against government action, and this purpose should guide its interpretation. Viewpoint: Individual Rights Primacy

• Constitution of the United States - History
• Constitution of the United States - Debate
• Constitution of the United States - Legal Consensus
• United States of America
• Bill of Rights
• Federalist Papers
• Articles of Confederation
• Judicial Review
• Constitutional Convention (1787)

1. U.S. Const. art. VII (ratification requirement of nine states).
2. Marbury v. Madison, 5 U.S. (1 Cranch) 137 (1803) (establishing judicial review).
3. Pauline Maier, Ratification: The People Debate the Constitution, 1787-1788 (Simon & Schuster, 2010).
4. Alexander Hamilton, James Madison, and John Jay, The Federalist Papers (1787-1788).
5. Antonin Scalia, A Matter of Interpretation: Federal Courts and the Law (Princeton University Press, 1997) (originalism).
6. David A. Strauss, The Living Constitution (Oxford University Press, 2010) (living constitutionalism).