This work presents the first complete modern edition and translation of the medieval Welsh medical recipes found in four fourteenth-century manuscripts, which have traditionally been ascribed to the Physicians of Myddfai. This comprises the entire corpus of Welsh medical recipes of this period, which offer practical treatments for a variety of commonly-occurring medical conditions such as toothache, constipation and gout. Each recipe is furnished with a note explaining the theory behind the advice given, providing analogous advice in older and contemporary medical texts, and where possible tracing the sources of this advice. This serves to locate the medieval Welsh medical recipes within the larger European tradition of medieval medicine, and the recipes are demonstrably an iteration of that tradition. A series of comprehensive glossaries allow the reader to find any recipe based on the materials used in it or the condition treated.