San Callisto is a Roman Catholic titular church in Rome, Italy, built over the site of Pope Callixtus I's martyrdom.

Pope Callixtus I, also called Callistus I, was the bishop of Rome from c. 218 to his death c. 222 or 223. He lived during the reigns of the Roman emperors Elagabalus and Alexander Severus. Eusebius and the Liberian catalogue list his episcopate as having lasted five years (217–222). In 217, when Callixtus followed Zephyrinus as Bishop of Rome, he started to admit into the Church converts from sects or schisms. He was killed for being Christian and is venerated as a saint by the Catholic Church.