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. However, private international law has no real connection with public international law, and is instead a feature of municipal 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 - along with other German-speaking countries) - and Scotland.

Within the federal systems where legal conflicts among federal states require resolution, as in the United States, the term conflict of laws is preferred simply because such cases do not involve an international issue. Hence, conflict of laws is a general term to refer to disparities among laws, regardless of whether the relevant legal systems are international or inter-state. The term, however, can be misleading when it refers to resolution of conflicts between competing systems rather than "conflict" itself. The term conflict of laws is usually used by common law countries, while for civil law countries the term private international law is more appropriate. The term private international law was coined by American lawyer and judge Joseph Story, but was abandoned subsequently by common law scholars and embraced by civil law lawyers.

The first instances of conflict of laws in the Western legal tradition can be traced to Greek law. Ancient Greeks dealt straightforwardly with multistate problems, and did not create choice-of-law rules. Leading solutions varied between the creation of courts for international cases, or application of local law, on the grounds that it was equally available to citizens of all states.

More significant developments can be traced to Roman law. Roman civil law (jus civile) being inapplicable to non-citizens, special tribunals had jurisdiction to deal with multistate cases. The officers of these specialized tribunals were known as the praetor peregrini. The Praetor peregrini did not select a jurisdiction whose rules of law should apply. Instead, they "applied" the "jus gentium." The jus gentium was a flexible and loosely-defined body of law based on international norms. Thus the praetor peregrini essentially created new substantive law for each case. Today, this is called a "substantive" solution to the choice-of-law issue.

The modern conflict of laws is generally considered to have begun in Northern Italy during the late Middle Ages and in particular at trading cities such as Genoa, Pisa and Venice. The need to adjudicate issues involving commercial transactions between traders belonging to different cities led to the development of the theory of statuta, whereby certain city laws would be considered as statuta personalia "following" the person whereby it may act, and other city laws would be considered as statuta realia, resulting in application of the law of the city where e.g. the res would be located (cf. lex rei sitae).

Maritime law was also a great driver of international legal rules; providing for the enforcement of contracts, the protection of shipwrecked sailors and property, and the maintaining of harbours.

The modern field of conflicts emerged in the United States during the 19th century with the publishing of Joseph Story's treatise on the Conflict of Laws in 1834. Story's work had a great influence on the subsequent development of the field in England such as those written by A.V. Dicey. Much of the English law then became the basis for conflict of laws for most commonwealth countries.

However, in the U.S., Story's work fell out of fashion in the mid-20th century. Traditional conflict of law rules were widely perceived as too rigid and unresponsive to the needs of a highly mobile society undergoing the Second Industrial Revolution. They were replaced with a number of approaches, of which the most important is the governmental interests analysis pioneered by law professor Brainerd Currie in a landmark series of essays. As a result of Currie's work, the rules for conflict of laws in the United States have diverged significantly from the rules in use at the international level.