An approach to grammatical theory developed by Alan Prince of Rutgers University, Paul Smolensky of Johns Hopkins, and John McCarthy of UMass.

In Optimality Theory, the calculation of grammatical well-formedness is accomplished by the optimization of a set of constraints on structure and on input-output disparity, instead of through serial application of rules subject and filtering constraints. The constraints of Optimality Theory are considered to be universal to all human languages, with conflicts between them being adjudicated by prioritization or ranking, Optimality Theory presents a grammatical architecture rather than an approach to a particular subdomain and so has consequences for many areas of linguistic and psycholinguistic analysis.