Civil law is a legal system inspired by Roman law, the primary feature of which is that laws are written into a collection, codified, and not (as in common law) determined by judges. Conceptually, it is the group of legal ideas and systems ultimately derived from the Code of Justinian, but heavily overlaid by Germanic, ecclesiastical, feudal, and local practices, as well as doctrinal strains such as natural law, codification, and legislative positivism. Materially, civil law proceeds from abstractions, formulates general principles, and distinguishes substantive rules from procedural rules. It holds legislation as the primary source of law, and the court system is usually inquisitorial, unbound by precedent, and composed of specially-trained judicial officers with a limited ability to interpret law.

The principle of civil law is to provide all citizens with an accessible and written collection of the laws which apply to them and which judges must follow. It is the most prevalent and oldest surviving legal system in the world. Colonial expansion spread the civil law system and European civil law has been adopted in much of Latin America as well as in parts of Asia and Africa. The primary source of law is the legal code, which is a compendium of statutes, arranged by subject matter in some pre-specified order; a code may also be described as "a systematic collection of interrelated articles written in a terse, staccato style." Law codes are usually created by a legislature's enactment of a new statute that embodies all the old statutes relating to the subject and including changes necessitated by court decisions. In some cases, the change results in a new statutory concept. The two other major legal systems in the world are common law and Islamic law.

Civil law systems may be subdivided into further categories:

• Countries where Roman law in some form is still living law and there has been no attempt to create a civil code: Andorra and San Marino
• Countries with mixed systems in which Roman law is an academic source of authority but common law is also influential: Scotland and the Roman-Dutch law countries (South Africa, Zambia, Zimbabwe, Sri Lanka and Guyana)
• Countries with codes intended to be comprehensive, such as France: it is this last category that is normally regarded as typical of "civil law" systems, and is discussed in the rest of this article.

The Scandinavian systems are of an intermediate character, as they have a background of Roman and customary law together with partial codification. The laws of Louisiana and Quebec may also be considered as hybrid systems, in that a French-type civil code coexists with pre-revolutionary French customary law and considerable common law influence.

A prominent example of civil law would be the Napoleonic Code (1804), named after French emperor Napoleon Bonaparte. The Code comprises three components: the law of persons, property law, and commercial law. Rather than a catalog of judicial decisions, the Code consists of abstractly written principles as rules of law.

Civil law is sometimes referred to as neo-Roman law, Romano-Germanic law or Continental law. The expression civil law is a translation of Latin jus civile, or "citizens' law", which was the Late Imperial term for its legal system, as opposed to the laws governing conquered peoples (jus gentium).