In enzymology, a galactosylgalactosylglucosylceramidase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are D-galactosyl-D-galactosyl-D-glucosyl-N-acylsphingosine and H<sub>2</sub>O, whereas its two products are D-galactose and lactosyl-N-acylsphingosine.
This enzyme belongs to the family of hydrolases, specifically those glycosidases that hydrolyse O- and S-glycosyl compounds. The systematic name of this enzyme class is D-galactosyl-D-galactosyl-D-glucosyl-N-acylsphingosine galactohydrolase. Other names in common use include trihexosyl ceramide galactosidase, ceramide trihexosidase, ceramidetrihexoside alpha-galactosidase, trihexosylceramide alpha-galactosidase, and ceramidetrihexosidase.