脑硫脂（sulfatide、硫酸脑苷脂、硫苷脂、硫脂类、半乳糖酰基鞘氨醇/3-O-sulfogalactosylceramide、SM4、硫酸化半乳糖/sulfated galactocerebroside）属于硫脂一类，具体上是"硫酸糖脂"（sulfoglycolipid）的一类，因其含硫酸基糖脂。脑硫脂的合成主要在内质网开始而在高尔基体结束，过程中神经酰胺转化成半乳糖之后硫化为脑硫脂。在髓磷脂的半乳糖脂中，有1/5是脑硫脂。脑硫脂主要被发现在由中枢神经系统的少突胶质细胞及周围神经系统中，施旺细胞所产生髓鞘细胞膜的胞膜外片上。然而，脑硫脂也存在于真核生物组织的许多细胞之细胞膜的胞膜外片上。

Sulfatide, also known as 3-O-sulfogalactosylceramide, SM4, or sulfated galactocerebroside, is a class of sulfolipids, specifically a class of sulfoglycolipids, which are glycolipids that contain a sulfate group. Sulfatide is synthesized primarily starting in the endoplasmic reticulum and ending in the Golgi apparatus where ceramide is converted to galactocerebroside and later sulfated to make sulfatide. Of all of the galactolipids that are found in the myelin sheath, one fifth of them are sulfatide. Sulfatide is primarily found on the extracellular leaflet of the myelin plasma membrane produced by the oligodendrocytes in the central nervous system and in the Schwann cells in the peripheral nervous system. However, sulfatide is also present on the extracellular leaflet of the plasma membrane of many cells in eukaryotic organisms.