黏液素（英语：Mucins，或简称黏素）是一类高分子量蛋白家族，且高度糖基化（属于糖缀合物），在大部分后生动物的上皮组织中都有表达黏液素的特色是它可以构成胶状物；因此在体内分泌的胶状分泌物扮演中要角色，可以润滑、协助细胞传讯，及构筑化学障壁，通常扮演身体屏障的角色。 Some mucins are associated with controlling mineralization, including nacre formation in mollusks, calcification in echinoderms and bone formation in vertebrates. They bind to pathogens as part of the immune system. Overexpression of the mucin proteins, especially MUC1, is associated with many types of cancer.

Mucins (/ˈmjuːsᵻn/) are a family of high molecular weight, heavily glycosylated proteins (glycoconjugates) produced by epithelial tissues in most organisms of Kingdom Animalia. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell signalling to forming chemical barriers. They often take an inhibitory role. Some mucins are associated with controlling mineralization, including nacre formation in mollusks, calcification in echinoderms and bone formation in vertebrates. They bind to pathogens as part of the immune system. Overexpression of the mucin proteins, especially MUC1, is associated with many types of cancer.