Promissory estoppel is an equitable theory of recovery that permits enforcement of a promise when one or more elements necessary to create an enforceable contract are missing.

The elements of promissory estoppel are generally: (1) a promise; (2) foreseeability of reliance by the promisor; (3) substantial and reasonable reliance by the promisee to its detriment; and (4) enforcing the promise is necessary to avoid injustice.

In Oklahoma, promissory estoppel serves as a legal remedy that allows a court to enforce a promise even when a formal contract does not exist or certain elements for a binding contract are absent. The doctrine is based on the principle of fairness and seeks to prevent injustice that would result if the promise were not enforced. The elements required to establish promissory estoppel in Oklahoma include: (1) a clear and definite promise by the promisor, (2) the promisor's expectation or foreseeability that the promisee will rely on the promise, (3) actual and reasonable reliance on the promise by the promisee to their detriment, and (4) a finding that enforcement of the promise is necessary to avoid an injustice. If these elements are met, Oklahoma courts may compel the promisor to fulfill the promise or provide compensation for the promisee's reliance. This equitable doctrine is applied at the discretion of the court and is intended to uphold the integrity of promises in situations where the technical requirements of contract law are not satisfied.