加护病房（英文：Intensive Care Unit，缩写：ICU）又称重症监护室（大陆）、加护病房（**），是医院内为需要高度密集医疗照料的重病伤患所特设的病房。为避免来自外界的干扰及感染，加护病房采密闭式设计，对访客入内及会面时间皆有严格限制。加护病房内设有诸多设备与仪器以随时监测患者的身体变化，并由医疗人员24小时轮班照顾。

加护病房的概念最早是由位于德国汉诺威的达特茅斯·希区考克医学中心的外科医生William Mosenthal所提出。

An intensive care unit (ICU), also known as an intensive therapy unit or intensive treatment unit (ITU) or critical care unit (CCU), is a special department of a hospital or health care facility that provides intensive treatment medicine.

Intensive care units cater to patients with severe and life-threatening illnesses and injuries, which require constant, close monitoring and support from specialist equipment and medications in order to ensure normal bodily functions. They are staffed by highly trained doctors and nurses who specialise in caring for critically ill patients. ICU's are also distinguished from normal hospital wards by a higher staff-to-patient ratio and access to advanced medical resources and equipment that is not routinely available elsewhere. Common conditions that are treated within ICUs include ARDS, trauma, multiple organ failure and sepsis.