Hyaluronan (also called hyaluronic acid or hyaluronate) is an anionic, non-sulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglycans in that it is unsulfated, forms in the plasma membrane instead of the Golgi and can be very large with its molecular weight often reaching the millions.

One of the chief components of the extracellular matrix, hyaluronan contributes significantly to cell proliferation and migration, and may also be involved in the progression of some malignant tumors. The average 70 kg (154 lbs) person has roughly 15 grams of hyaluronan in their body, one-third of which is turned over (degraded and synthesized) every day. 

Hyaluronic acid is also a component of the group A streptococcal extracellular capsule, and is believed to play a role in virulence.