To introduce the Web Book of Regional Science it is first necessary to explain the basics of the field of Regional Science. For regional scientists, a region is in most instances a geographical area smaller than the nation in which it is found. So a region might be a city, a county, a group of counties or a state. Regions often defy governmental boundaries, as when the issue under study relates to a labor market area or a watershed. Social scientists have studied regions for hundreds of years, but it wasn’t until the 1954 formation of the Regional Science Association that Regional Science became formally recognized as an interdisciplinary field of scholarly endeavor. The existence of RSA (now Regional Science Association International) and its progeny (several “regional” and “superregional” regional science associations) fosters better codification of methods and exchange of frontier ideas from such fields as geography, sociology, planning, statistics, and economics. The Web Book of Regional Science continues the process of codification and exchange by bringing together on one web site comprehensive descriptions of many of the basic concepts, analytical tools and policy issues important to regional science.