Fault may refer to:

• Geologic fault, planar rock fractures which show evidence of relative movement.
• Fault (technology), an abnormal condition or defect at the component, equipment, or sub-system level which may lead to a failure.
• Fault (dog), in animal breeding, is a conformation point whose state or quality falls outside of the acceptable range for the attribute being judged.
• In tennis, a fault could be either a foot fault or a service fault, where an aspect of the server's serve is not in line with the rules of the game.