Aminosalicylic acid (C₇H₇NO₃) is also known as para-aminosalicylic acid, p-aminosalicylic acid or 4-aminosalicylic acid; abbreviated 4-ASA, PAS or P. It is sold in the US by Jacobus Pharmaceutical as Paser®.

5-aminosalicylic acid is a closely related compound that also has medical uses.

Aminosalicylic acid is an antibiotic used to treat tuberculosis. It has been use for over forty years in the treatment of Inflammatory Bowel Diseases (IBDs), where it has shown greater potency in Crohn's Disease. It is thought to act via NF-kB (Nuclear Factor Kappa B) inhibition and free radical scavenging.