A disaster is an unexpected natural or man-made catastrophe of substantial extent causing significant property damage or destruction, loss of life or sometimes permanent changes to the natural environment. Disasters may also be unforeseen events which devastate a company or industry, such as a public relations disaster or a major flop. A disaster can create huge financial losses and protection against losses due to disasters is one purpose of insurance.
'Disaster' comes from the Italian desastro, which means "unfavourable to one's stars", ultimately from the Greek astron (star), and reflects the key characteristic of a disaster which is its unintentional nature. Catastrophes which are intentional, such as terrorist attacks, are often called man-made or technological disasters.
A disaster in database terminology is a loss of data which cannot be recovered.
See also: Business continuity planning