The Manchurian bush warbler (Horornis borealis), also known as Korean bush warbler, is a species of bush warbler in the Cettiidae family. It is found in China, Hong Kong, India, North Korea, South Korea, Laos, the Philippines, Russia, Thailand, and Vietnam. The estimated distribution size is reported to be a large range - approximately 1,610,000 km². Although the global population has not been measured, the population trend appears to be stable. Because of this, the Manchurian bush warbler is evaluated as a least concern species.