Conflict of laws (or private international law) is a set of procedural rules that determines which legal system and which jurisdiction's applies to a given dispute. The rules typically apply when a legal dispute has a "foreign" element such as a contract agreed to by parties located in different countries, although the "foreign" element also exists in multi-jurisdictional countries such as the United Kingdom, the United States, Australia and Canada.

The term conflict of laws itself originates from situations where the ultimate outcome of a legal dispute depended upon which law applied, and the common law courts manner of resolving the conflict between those laws. In civil law, lawyers and legal scholars refer to conflict of laws as private international law. Private international law has no real connection with public international law, and is instead a feature of local law which varies from country to country.

The three branches of conflict of laws are

Its three different names – conflict of laws, private international law, and international private law – are generally interchangeable, although none of them is wholly accurate or properly descriptive. The term conflict of laws is primarily used in jurisdictions of the Common Law legal tradition, such as in the United States, England, Canada, and Australia. Private international law (droit international privé) is used in France, as well as in Italy, Greece, and the Spanish- and Portuguese-speaking countries. International private law (internationales Privatrecht) is used in Germany (as well as Austria, Leichtenstein and Switzerland), Russia and Scotland.