The Roman legal tradition is one of the most consequential contributions to subsequent civilization that tends to get underemphasized in popular accounts of Rome's legacy. Roman law, preserved and systematized in Justinian's Corpus Juris Civilis (compiled 529-534 AD), became the foundation of civil law systems across most of Europe and the world.

The development of Roman law over the Republic and Empire was a continuous process of refinement, debate, and systematization. The Twelve Tables (c. 450 BC) were the first written Roman law code — a relatively simple text covering property, inheritance, and procedure. By the classical period (1st-3rd centuries AD), Roman jurisprudence had developed a sophisticated body of doctrine covering contracts, property, family law, obligations, and procedure, developed through the opinions of authoritative jurists.

The distinction between ius civile (civil law, applying to Roman citizens) and ius gentium (law of peoples, applying to non-citizens) was an early recognition of the need for a legal framework that could handle disputes between people of different legal statuses. The ius gentium was developed largely by the praetor peregrinus (the magistrate handling cases involving non-citizens) and reflected commercial reality rather than strict Roman tradition.

The concept of legal personality — distinguishing between a person (a legal subject with rights and duties) and a natural human being — was a Roman invention with enormous consequences. Corporations, trusts, and other artificial persons that we now take for granted as basic legal entities were first theorized within the Roman legal tradition.