Ceramide glucosyltransferase (or glucosylceramide synthase) is a glucosyltransferase enzyme involved in the production of glucocerebrosides (also called glucosylceramides). It is responsible for the first step in synthesis of all glycosphingolipids—critical components of cell membranes—from sphingolipids, attaching a glucose molecule (glycosylation) to produce a glucocerebroside product. The enzyme is classified under EC 2.4.1.80.