The most important historian of the early Roman Empire, Tacitus (Cornelius), a famous Roman historian, was born in 55, 56, or 57 AD and lived until about 120. He became an orator, married in 77 a daughter of Julius Agricola before Agricola went to Britain, served as a tribune in 81 or 82, became a senator under the Flavian emperors, and was praetor in 88. After four years of absence, he experienced the horrors of the final years of Emperor Domitian and turned to the writing of history. He was consul in 97. A close friend of the younger Pliny, together they successfully denounced Marius Priscus.

Works: (i) The Life and Character of Agricola, written in 97–98, particularly interesting due to Agricola's career in Britain. (ii) Germania (98–99), an equally important description of the geography, anthropology, products, institutions, and social life and tribes of the Germans as known to the Romans. (iii) Dialogue on Rhetoric (Dialogus), of unknown date; a lively discussion on the decline of rhetoric and education. (iv) Histories (probably published in parts from 105 onwards), a large work that originally consisted of at least twelve books covering the period 69–96 AD, but only Books 1–4 and part of Book 5 have been preserved, dealing in detail with the dramatic years 69–70. (v) Annals, Tacitus' other major work, which originally covered the period 14–68 AD (Emperors Tiberius, Gaius, Claudius, Nero) and was published between 115 and about 120. Of the sixteen books, at least Books 1–4 (covering the years 14–28), a piece of Book 5, and the entirety of Book 6 (31–37), part of Book 11 (from 47), Books 12–15, and part of Book 16 (up to 66) have been preserved.

Tacitus is known for the development of a comprehensive, concise style, character study and psychological analysis, as well as for his often grim history told in a masterful manner. As a historian of the early Roman Empire, he is unmatched. The Loeb Classical Library edition of Tacitus is in five volumes.