Organic chemistry is the science of carbon-containing compounds. There are four major types of reactive intermediates in organic chemistry: carbocations, carboanions, radicals and carbenes. Therefore, carbocation chemistry is not only fundamental to the advancement of organic chemistry, it also has found widespread applications in organic synthesis. It is not an exaggeration to say that carbocation chemistry is part of the foundation of organic chemistry. This book provides a panoramic view of carbocation chemistry with an emphasis on synthetic applications.