A rationalis was a high-ranking fiscal officer in the Roman Empire. Until replaced by the comes sacrarum largitionum by Emperor Constantine in the early 4th century, the rationalis summarum – comparable to a modern-day finance minister – was one of two state officials who had authority over the imperial treasury, the other one being the rationalis rei privatae. Examples for tasks that were performed by a rationalis are "the collection of all normal taxes and duties, the control of currency and the administration of mines and mints".