神经退行性疾病 ，又称为神经退化性疾病，是一种大脑和脊髓的细胞神经元丧失的疾病状态。大脑和脊髓由神经元组成，神经元有不同的功能，如控制运动，处理感觉信息，并作出决策。大脑和脊髓的细胞一般是不会再生的，所以过度的损害可能是毁灭性的，不可逆转的。神经退行性疾病是由神经元或其髓鞘的丧失所致, 随着时间的推移而恶化，以导致功能障碍。

神经退行性疾按表型分为两组：

Neurodegeneration is the umbrella term for the progressive loss of structure or function of neurons, including death of neurons. Many neurodegenerative diseases including amyotrophic lateral sclerosis, Parkinson's, Alzheimer's, and Huntington's occur as a result of neurodegenerative processes. Such diseases are incurable, resulting in progressive degeneration and/or death of neuron cells. As research progresses, many similarities appear that relate these diseases to one another on a sub-cellular level. Discovering these similarities offers hope for therapeutic advances that could ameliorate many diseases simultaneously. There are many parallels between different neurodegenerative disorders including atypical protein assemblies as well as induced cell death. Neurodegeneration can be found in many different levels of neuronal circuitry ranging from molecular to systemic.