The Nine Chapters on the Mathematical Art is a classic text: the most important mathematical source in China during the past 2000 years, and comparable in significance to Euclid's Elements in the West. This volume contains the first complete English translation of the Nine Chapters, togetherwith two commentaries written in the 3rd and 7th centuries AD, and a further commentary by the translators. The Nine Chapters contains 246 problems and their solutions, which fall into nine categories that are firmly based on practical needs. There are methods for solving problems in areas such asland measurement, construction, agriculture, commerce, and taxation. The Chinese commentators provided the algorithms needed to solve the problems, and explanations of how the algorithms work. The translators' commentary provides clear and accessible background material for the Western reader,explanations of technicalities, and notes on the treatment of similar or identical mathematical problems in other countries. The Nine Chapters quickly acquired a distinguished reputation, and was the standard mathematics textbook in China and the surrounding regions until Western science wasintroduced in about 1600. This English translation gives the reader an idea of the distinctive style and important contributions of traditional Chinese mathematics.