This monograph, which is the first to be devoted to the geometry of multidimensional three-webs, presents the classical adn up-to-date results of the theory, and those parts of geometry and algebra which are closely connected with it. Many problems of the theory of smooth quasigroups and loops are considered. In addition to the general theory of webs, important classes of special webs are also studied. The volume contains eight chapters dealing with geometric and algebraic structures associated with three-webs, transversally geodesic and isoclinic three-webs, Bol and Moufang three-webs, closed G-structures, automorphisms of three-webs, the geometry of the fourth-order differential neighborhood of a multidimensional three-web, and d-webs of codimension r. The book concludes with some appendices and a comprehensive bibliography. This volume will be of particular interest to graduate students and researchers working in the areas of differential and algebraic geometry and algebra.