Crisis of faith is a term commonly applied to periods of intense doubt and internal conflict about one's preconceived beliefs or life decisions. A crisis of faith can be contrasted to simply a period of doubt in that a crisis of faith demands reconciliation or reevaluation before one can continue believing in whichever tenet is in doubt or continuing in whatever life path is in question - i.e. the crisis necessitates a non-compromisable decision: either sufficiently reconcile the cause of doubt with the belief or decision in question, or drop the belief.

The concept of a crisis of faith is most commonly applied to religious beliefs, since faith is a fundamental tenet of many religions and the gravity of religious decisions is perceived by many to be great enough to aptly describe a period of extreme doubt as a "crisis". It can also be applied to doubts over influential life decisions, such as doubts over a chosen career, a marriage partner, etc.