Junius is the nomen of the gens Junia, an important and very ancient family of ancient Rome, with both Patrician and Plebeian branches. Many notable members of the family bore the cognomen Brutus.

Junius was the pseudonym of a writer who contributed a series of letters to the Public Advertiser,The Public Advertiser was a political newspaper run by Henry Sampson Woodfall, based in London. His brother William Woodfall later established the Daily, a paper that reported on parliamentary debates. from January 21 1769 to January 21 1772. The signature had been already used, apparently by him, in a letter of November 21 1768.