新城病（英文：Newcastle disease）是一种禽鸟传染病，由新城病病毒引致。此病毒在禽鸟间有很高的传染性和死亡率，现时没有治疗方法，但可以透过疫苗和消毒措施以减少其爆发之可能性。人类亦可能感染此病毒，导致轻微的结膜炎和类似流行性感冒之症状，但一般不构成生命威胁。新城病毒最早于1926年在印尼爪哇被发现，隔年又在英国泰恩河畔新堡被发现并以此得名，但1898年造成苏格兰西北部家禽大量死亡的病毒极有可能是新城病毒。此病毒流行于许多国家，最重要的影响即是造成家禽的感染，可造成大量经济损失。 新城病毒可能有制成抗癌药物的潜力，因为它可选择性的杀伤癌细胞而避免破坏正常的细胞。

Newcastle disease is a contagious bird disease affecting many domestic and wild avian species; it is transmissible to humans. It was first identified in Java, Indonesia, in 1926, and in 1927, in Newcastle-upon-Tyne, England (whence it got its name). However, it may have been prevalent as early as 1898, when a disease wiped out all the domestic fowl in northwest Scotland. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epizootic on the poultry industries. It is endemic to many countries.