A health crisis is an emergency or complex health system that affects the public in one or more geographic areas from a particular locality to encompass the entire planet. Health crises generally have significant impacts on community health, loss of life, and on the economy. They may result from disease, industrial processes or poor policy.

Its severity is often measured by the number of people affected by its geographical extent, or the disease or death of the pathogenic process which it originates.

Generally there are three key components in health crises: