This book is the outcome of a dream Jürgen Backhaus had several years ago, to endow the law and economics community with a new and broad resource, making available to scholars an accessible and “living” reference. While other valuable resources already exist, providing a number of essays on given topics, this encyclopedia is original in that it aims at offering a very broad array of short references within law and economics or tangential to the discipline. Indeed, a large number of these entries are at the limits of law and economics and other fields that are close to law and economics – public choice, institutional economics, transaction cost economics, industrial economics, etc. This reveals that law and economics is much more difficult to delineate than what is usually assumed. And there is nothing to surprise us here: laws, legal rules, and institutions are everywhere. They are the bases of human societies and at the core of economic activities. It is indeed almost impossible to be an economist without taking law and institutions into account. This is what we tried to do in this encyclopedia. Finally, also inspired by Jürgen Backhaus, we chose to make room for historical and methodological entries about the founders of the field and about some of the important scholars who, directly or indirectly, contributed to make law and economics what it became. These three dimensions reflect the parti pris that was chosen to build this book. They reflect our convictions about law and economics.