N-acetylgalactosamine-4-sulfatase (EC 3.1.6.12, chondroitinsulfatase, chondroitinase, arylsulfatase B, acetylgalactosamine 4-sulfatase, N-acetylgalactosamine 4-sulfate sulfohydrolase) is an enzyme with systematic name N-acetyl-<small>D</small>-galactosamine-4-sulfate 4-sulfohydrolase. It catalyses the following reaction:
It also acts on N-acetylglucosamine 4-sulfate.