:This article is about the Roman historian. For the Roman general who put down the rebellion of Boudica, see Gaius Suetonius Paulinus.

Gaius Suetonius Tranquillus (ca. 69/75 - after 130), also known as Suetonius, was a prominent Roman historian and biographer.

Suetonius was born the son of Suetonius Laetus, who probably came from Hippo Regius (Annaba, Algeria). Laetus was an equestrian who served and took part in the first Battle of Bedriacum for the Emperor Otho and against the future Emperor Vitellius in 69.

Suetonius was a close friend to Senator and letter writer Pliny the Younger. Pliny describes him as "quiet and studious, a man dedicated to writing." Pliny helped him buy a small property in Italy and interceded with the Emperor Trajan to grant Suetonius immunities usually granted to a father of three, the jus trium liberorum, because his marriage was childless. Through Pliny, Suetonius came into favour with Trajan and Hadrian.

Suetonius served on Pliny’s staff when Pliny was Proconsul of Bithynia Pontus (northern Asia Minor) between 110 and 112. Under Trajan he served as secretary of studies (precise functions are uncertain) and director of Imperial archives. Under Hadrian, he became the Emperor's secretary.

In 122, Hadrian dismissed him for disrespectful behaviour towards Empress Vibia Sabina. Suetonius may have later regained imperial favor under Hadrian and returned to his position. This hypothesis is based on the suggestion that Offices of State was one of his last works, and that the subject was chosen to reflect Hadrian's administrative reforms. However, there is no certain evidence for a public career after 122.

He is mainly remembered as the author of De Vita Caesarum ("Lives of the Caesars", best known in English as "The Twelve Caesars"), his only extant work except for the brief lives and other fragments noted below. The Twelve Caesars, probably written in Hadrian's time, is a collective biography of the Roman Empire's first leaders who were: Julius Caesar (the first few chapters are missing), Augustus, Tiberius, Caligula, Claudius, Nero, Galba, Otho, Vitellius, Vespasian, Titus and Domitian. The book was dedicated to a friend Gaius Septicius Clarus, a prefect of the Praetorian Guard in 119. The work tells the tale of each Caesar's life according to a set formula: the descriptions of appearance, omens, family history, quotes, and then a history are given in a consistent order for each Caesar. Suetonius regarded emperors who amassed wealth for the public purse to be "greedy", perhaps a reflection of the average Roman middle class attitudes.

*De Viris Illustribus ("On Famous Men" — in the field of literature), to which belong: **De Illustribus Grammaticis ("Lives Of The Grammarians"; 20 brief lives, apparently complete) **De Claris Rhetoribus ("Lives Of The Rhetoricians"; 5 brief lives out of an original 16 survive) **De Poetis ("Lives Of The Poets"; the life of Virgil, as well as fragments from the lives of Terence, Horace and Lucan, survive) **De historicis ("Lives of the historians"; a brief life of Pliny the Elder is attributed to this work) *Peri ton par' Hellesi paidion ("Greek Games") *Peri blasphemion ("Greek Terms of Abuse") The two last works were written in Greek. They apparently survive in part in the form of extracts in later Greek glossaries.

*Lives of Famous Whores *Royal Biographies *Roma ("On Rome"), in four parts: **Roman Manners & Customs **The Roman Year **The Roman Festivals **Roman Dress *Offices of State *On Cicero’s Republic *Physical Defects of Mankind *Methods of Reckoning Time *An Essay on Nature *Grammatical Problems *Critical Signs Used in Books

*The Lives of the Twelve Caesars at LacusCurtius (Latin original, English translation) *Suetonius' works at Latin Library (Latin) * **The Lives of the Twelve Caesars at Project Gutenberg (English translation - includes Lives Of The Grammarians, Rhetoricians, And Poets) *Suetonius and the reign of Tiberius: a comparison with other sources *Gai Suetoni Tranquilli De vita Caesarum libri III-VI Cornell University Library Historical Monographs Collection. {Reprinted by} Cornell University Library Digital Collections

*Barry Baldwin, Suetonius: Biographer of the Caesars. Amsterdam: A. M. Hakkert, 1983.