Hepatitis (plural: hepatitides) is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar, the genitive of which, meaning of the liver, and suffix -itis, meaning "inflammation" (c. 1727). The condition can be self-limiting (healing on its own) or can progress to fibrosis (scarring) and cirrhosis.

Hepatitis may occur with limited or no symptoms, but often leads to jaundice, anorexia (poor appetite) and malaise. Hepatitis is acute when it lasts less than six months and chronic when it persists longer. Worldwide, hepatitis viruses are the most common cause of the condition, but hepatitis can be caused by other infections, toxic substances (notably alcohol, certain medications, some industrial organic solvents and plants), and autoimmune diseases.