亨丁顿舞蹈症（英语：Huntington's disease，缩写：HD），又译亨廷顿舞蹈症、杭丁顿舞蹈症等，是一种遗传性神经退行性疾病，起因于第4对染色体CAG串行异常大量重复，病发时会无法控制四肢，就像手舞足蹈一样，并伴随着智能减退，最后因吞咽、呼吸困难等原因而死亡。该疾病由美国医学家乔治·亨丁顿于1872年发现，因而得名。这种病在欧美的出现率比在亚洲高，但香港也有不少病例。该疾病的症状通常于同一家庭的成员间遗传，原则上可猜测子代的发病与否。最初的症状常常是一些情绪或认知上细微的问题。患者普遍缺乏协调性、步态不稳等症状。随着病情的进展，不协调、不平稳的肢体动作变得更加明显可见，并且会伴随心理和行为能力的下降。患者的体能会逐渐恶化，最后导致运动协调困难，而心理能力普遍下降至阿兹海默症的程度。肺炎、心脏疾病、跌倒的物理损伤等并发症，使发病后的寿命约只剩下15年。症状可以开始于任一年龄，但通常于40岁左右发病。约6％的病例为21岁之前发生运动不能刚性综合症，这类患者症状发展较快、并略有不同。此种变种症状被列为青少年亨丁顿舞蹈症、或 Westphal 变种亨丁顿舞蹈症。

Huntington's disease (HD) is a neurodegenerative genetic disorder that affects muscle coordination and leads to mental decline and behavioral symptoms. Symptoms of the disease can vary between individuals and affected members of the same family, but usually progress predictably. The earliest symptoms are often subtle problems with mood or cognition. A general lack of coordination and an unsteady gait often follow. As the disease advances, uncoordinated, jerky body movements become more apparent, along with a decline in mental abilities and behavioral symptoms. Physical abilities gradually worsen until coordinated movement becomes difficult. Mental abilities generally decline into dementia. Complications such as pneumonia, heart disease, and physical injury from falls reduce life expectancy to around twenty years from the point at which symptoms begin. Physical symptoms can begin at any age from infancy to old age, but usually begin between 35 and 44 years of age. The disease may develop earlier in life in each successive generation. About 6% of cases start before the age of 21 years with an akinetic-rigid syndrome; they progress faster and vary slightly. The variant is classified as juvenile, akinetic-rigid, or Westphal variant HD.