A law report or reporter is a compilation of judicial opinions from a selection of case law decided by courts. These reports serve as published records of judicial decisions that are cited by lawyers and judges for their use as precedent in subsequent cases.

Historically, the term "reporter" was used to refer to the individuals responsible for compiling, editing, and publishing these opinions. For example, the Reporter of Decisions of the Supreme Court of the United States is the person authorized to publish the Court's cases in the bound volumes of the United States Reports. Today, in American English, "reporter" also refers to the books themselves. In Commonwealth English, these are described by the plural term "law reports", the title that usually appears on the covers of the periodical parts and the individual volumes.

In common law jurisdictions, such as the United States, the doctrine of stare decisis ("to stand by things decided") requires courts to follow precedent by applying legal principles established in prior decisions by higher courts within the same jurisdiction. The system of precedent relies heavily on written opinions issued by appellate and supreme courts, and occasionally by trial courts, as these opinions enable judges and lawyers to reference and compare reasoning in cases involving similar factual circumstances.

Official law reports or reporters are those authorized for publication by statute or other governmental ruling. Governments designate law reports as official to provide an authoritative, consistent, and authentic statement of a jurisdiction's primary law. Official case law publishing may be carried out by a government agency, or by a commercial entity. Unofficial law reports, on the other hand, are not officially sanctioned and are published as a commercial enterprise. In Australia and New Zealand (see below), official reports are called authorised reports—unofficial reports are referred to as unauthorised reports.

For the publishers of unofficial reports to maintain a competitive advantage over the official ones, unofficial reports usually provide helpful research aids (e.g., summaries, indexes), like the editorial enhancements used in the West American Digest System. Some commercial publishers also provide court opinions in searchable online databases that are part of larger fee-based, online legal research systems, such as Westlaw, Lexis-Nexis or Justis.

Unofficially published court opinions are also often published before the official opinions, so lawyers and law journals must cite the unofficial report until the case comes out in the official report. But once a court opinion is officially published, case citation rules usually require a person to cite to the official reports.

A good printed law report in traditional form usually contains the following items:

It is only the last item that is authoritative. The others, although useful for its understanding, are only the law reporter's contribution. Thus, law students are warned that the headnote is not part of the decision rendered, since headnotes occasionally contain misinterpretations of the law, and are not part of the official judgment. (In the United States, however, the headnote, also called the syllabus, is sometimes written by the court itself, and this is noted.)