Kawasaki disease (also known as mucocutaneous lymph node syndrome) is a syndrome of unknown cause that results in a fever and mainly affects children under 5 years of age. It is a form of vasculitis, where medium-sized blood vessels become inflamed throughout the body. The fever typically lasts for more than five days and is not affected by usual medications. Other common symptoms include large lymph nodes in the neck, a rash in the genital area, lips, palms, or soles of the feet, and red eyes. Within three weeks of the onset, the skin from the hands and feet may peel, after which recovery typically occurs. The disease is the leading cause of acquired heart disease in children in developed countries, which include the formation of coronary artery aneurysms and myocarditis.

While the specific cause is unknown, it is thought to result from an excessive immune system response to an infection in children who are genetically predisposed. It does not spread between people. Diagnosis is usually based on a person's signs and symptoms. Other tests such as an ultrasound of the heart and blood tests may support the diagnosis. Diagnosis must take into account many other conditions that may present similar features, including scarlet fever and juvenile rheumatoid arthritis. An emerging 'Kawasaki-like' disease temporally associated with COVID-19 appears to be a distinct syndrome.

Typically, initial treatment of Kawasaki disease consists of high doses of aspirin and immunoglobulin. Usually, with treatment, fever resolves within 24 hours and full recovery occurs. If the coronary arteries are involved, ongoing treatment or surgery may occasionally be required. Without treatment, coronary artery aneurysms occur in up to 25% and about 1% die. With treatment, the risk of death is reduced to 0.17%. People who have had coronary artery aneurysms after Kawasaki disease require lifelong cardiological monitoring by specialized teams.

Kawasaki disease is rare. It affects between 8 and 67 per 100,000 people under the age of five except in Japan, where it affects 124 per 100,000. Boys are more commonly affected than girls. The disorder is named after Japanese pediatrician Tomisaku Kawasaki, who first described it in 1967.