沸水反应炉（英语：boiling water reactor, BWR）是一种用来发电的轻水反应炉。沸水反应炉是第二常见的核能发电反应炉型式，在五十年代中期由爱达荷国家实验室（Idaho National Laboratory）与通用电气公司共同研发成功。现在主要制造厂商是专门设计与建造这类反应炉的GE日立核能（GE Hitachi Nuclear Energy）。

The boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR), also a type of light water nuclear reactor. The main difference between a BWR and PWR is that in a BWR, the reactor core heats water, which turns to steam and then drives a steam turbine. In a PWR, the reactor core heats water, which does not boil. This hot water then exchanges heat with a lower pressure water system, which turns to steam and drives the turbine. The BWR was developed by the Idaho National Laboratory and General Electric (GE) in the mid-1950s. The main present manufacturer is GE Hitachi Nuclear Energy, which specializes in the design and construction of this type of reactor.