Mea maxima culpa is a term of Latin origin meaning ‘through my most grievous fault’. It is used to acknowledge a mistake or wrongdoing. Mea maxima culpa is a stronger version of mea culpa, which means ‘through my fault’.
Mea maxima culpa is traditionally used in a prayer of confession in the Catholic Church as the third and most emphatic expression of guilt (‘mea culpa, mea culpa, mea maxima culpa’). Unlike mea culpa, mea maxima culpa is rarely used outside of a religious context.