An oxocarbenium ion is a canonical form of a carbocation, real or hypothetical, which places a formal positive charge on an oxygen atom. They are common transition states for the hydrolysis of glycosidic bonds, and are a commonly used strategy for chemical glycosylation. These ions have since been proposed as transition states of a wide range of chemical transformations, and have been utilized in the total synthesis of several natural products. In addition, they commonly appear in mechanisms of enzyme-catalyzed biosynthesis and hydrolysis of carbohydrates in nature.