A field hospital is a temporary hospital or mobile medical unit that takes care of casualties on-site before they can be safely transported to more permanent facilities. This term was initially used in military medicine (such as the Mobile Army Surgical Hospital or MASH), but it has also been used to describe alternate care sites used in disasters and other emergency situations.

A field hospital is a medical staff with a mobile medical kit and, often, a wide tent-like shelter (at times an inflatable structure in modern usage) so that it can be readily set up near the source of casualties. In an urban environment, the field hospital is often established in an easily accessible and highly visible building (such as restaurants, schools, hotels and so on). In the case of an airborne structure, the mobile medical kit is often placed in a normalized container; the container itself is then used as shelter. A field hospital is generally larger than a temporary aid station but smaller than a permanent military hospital.

International humanitarian law such as the Geneva Conventions include prohibitions on attacking doctors, ambulances, hospital ships, or field hospitals buildings displaying a Red Cross, a Red Crescent or other emblem related to the International Red Cross and Red Crescent Movement; deliberately attacking or otherwise causing harm on these health facilities (especially during warfare or armed conflicts) may constitute a war crime.

Field hospitals are also prevalent in the event of disease outbreaks and pandemics. The ongoing COVID-19 pandemic led to the establishment of field hospitals in many parts of the world, especially in the developing world.