A patent is the legal right of an inventor to exclude others from making or using a particular invention. This right is sometimes termed an ‘intellectual property right’ and is viewed as an encouragement for innovation. This article gives a brief history of patenting, and discusses the legal and administrative process for obtaining a patent in the major world jurisdictions. Evidence on patent effectiveness in encouraging innovation is surveyed, and the article concludes with a discussion of the use of patent data in economic analysis.