Medieval Wales had a separate system of law to that found in English, and the law has been preserved in several medieval manuscripts. Although the purpose of the law manuscripts was to explain the legal complexities, they were also works of literature, written in medieval Welsh. One aspect of the law manuscripts is the large collections of legal triads, basically sentences listing things in threes. These were probably composed for educational, mnemonic purposes, and offer a real insight into the workings of medieval Welsh law. This book is the first full study of the legal triads, an important part of medieval Welsh law. Triads were a feature in most medieval Welsh (and, indeed, Irish) literature, and there are large collections found of various genres. The legal triads are probably the largest collections of triads found in Welsh, and there are triads for almost every aspect of medieval Welsh law. This book sets the triads in their literary and legal context, gives a full edited text of the triads found in the law manuscripts as well as offering translations of the legal triads. There are also notes for each triad found in the legal triad collections, and this book will be a useful starting point for studying medieval Welsh law.