黄疸又称黄胆，俗称黄病，是一种因人体血液中的胆红素浓度增高，所引起的皮肤、黏膜和眼球巩膜等部份发黄的症状。某些肝脏病、胆囊病和血液病经常会引发黄疸的症状。患有高胆红素血症会导致细胞外液中的胆红素水平增加，正常血浆中胆红素浓度是低于 1.2 毫克/分升 （< 25µmol/L），当浓度高于约 3 毫克/分升 (> 50µmol/L）便会导致黄疸。

如变黄的皮肤是在手掌或脚掌，而不是巩膜（眼白）或粘膜（口腔），是因为胡萝卜素血症（血液中的胡萝卜素含量过高，对健康无碍），而并非黄疸。

Jaundice, also known as icterus, is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae (whites of the eyes), and other mucous membranes caused by high blood bilirubin levels. This hyperbilirubinemia causes increased levels of bilirubin in the extracellular fluid. Concentration of bilirubin in blood plasma is normally below 1.2 mg/dL (<25µmol/L). A concentration higher than approx. 3 mg/dL (>50µmol/L) leads to jaundice. The term jaundice is from the French word jaune, meaning yellow.