Titus Flavius T. f. T. n. Clemens was a nephew of the Roman Emperor Vespasian. He was the son of Titus Flavius Sabinus, consul in AD 52 and praefectus urbi during the reign of Nero, and a brother of Titus Flavius Sabinus, consul in AD 82. The emperors Titus and Domitian were his cousins.
As a child, Clemens was besieged along with his family in the capitol, when the soldiers of his uncle, Vespasian, were approaching Rome. His father was captured and slain by the forces of Vitellius, who burnt the capitol, but the rest of the family escaped.
Clemens' brother was consul with Domitian, shortly after the latter's accession, but the emperor put his cousin to death on the pretext that the herald proclaiming him consul had called him Imperator. In fact, the emperor was more likely motivated by his love for his cousin's wife, Julia Flavia (who, as the daughter of his brother Titus, was also his niece).
Clemens also married one of his cousins, Flavia Domitilla, daughter of Vespasian's daughter, Domitilla, who was thus also a niece of Domitian. They had two sons, whom Domitian intended to succeed him in the empire, renaming one of them Vespasian and the other Domitian. However, in AD 95, when Clemens and the emperor were consuls, Domitian had his cousin put to death.
According to Cassius Dio, Clemens was put to death on a charge of atheism, for which, he adds, many others who went over to the Jewish opinions were executed. This may imply that Clemens had become a Christian. For the same reason, his wife was banished to Pandataria.
To this Clemens in all probability is dedicated the church of St. Clement at Rome, on the Caelian hill, which is believed to have been built originally in the fifth century, although its site is now occupied by a more recent, though very ancient, structure. In the year 1725 Cardinal Annibal Albani found under this church an inscription in honour of Flavius Clemens, martyr, which is described in a work called T. Flavii Clementis Viri Consularis et Martyris Tumulus illustratis. Some connect Clemens with Clemens Romanus, the author of the Epistle to the Corinthians.