In law, common law (also known as judicial precedent, judge-made law, or case law) is the body of law created by judges and similar quasi-judicial tribunals by virtue of being stated in written opinions.

The defining characteristic of common law is that it arises as precedent. Common law courts look to the past decisions of courts to synthesize the legal principles of past cases. Stare decisis, the principle that cases should be decided according to consistent principled rules so that similar facts will yield similar results, lies at the heart of all common law systems. If a court finds that a similar dispute as the present one has been resolved in the past, the court is generally bound to follow the reasoning used in the prior decision. If, however, the court finds that the current dispute is fundamentally distinct from all previous cases (a "matter of first impression"), and legislative statutes are either silent or ambiguous on the question, judges have the authority and duty to resolve the issue. The opinion that a common law judge gives agglomerates with past decisions as precedent to bind future judges and litigants.

The common law, so named because it was "common" to all the king's courts across England, originated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire later spread the English legal system to its colonies, many of which retain the common law system today. These common law systems are legal systems that give great weight to judicial precedent, and to the style of reasoning inherited from the English legal system.

The term "common law", referring to the body of law made by the judiciary, is often distinguished from statutory law and regulations, which are laws adopted by the legislature and executive respectively. In legal systems that recognise the common law, judicial precedent stands in contrast to and on equal footing with statutes. The other major legal system used by countries is the civil law, which codifies its legal principles into legal codes and does not recognise judicial opinions as binding.

Today, one-third of the world's population lives in common law jurisdictions or in mixed legal systems that combine the common law with the civil law, including Antigua and Barbuda, Australia, Bahamas, Bangladesh, Barbados, Belize, Botswana, Burma, Cameroon, Canada (both the federal system and all its provinces except Quebec), Cyprus, Dominica, Fiji, Ghana, Grenada, Guyana, Hong Kong, India, Ireland, Israel, Jamaica, Kenya, Liberia, Malaysia, Malta, Marshall Islands, Micronesia, Namibia, Nauru, New Zealand, Nigeria, Pakistan, Palau, Papua New Guinea, Philippines, Sierra Leone, Singapore, South Africa, Sri Lanka, Trinidad and Tobago, the United Kingdom (including its overseas territories such as Gibraltar), the United States (both the federal system and 49 of its 50 states), and Zimbabwe.