An archivist was an information professional who assessed, collected, organized, preserved, maintained control over, and provided access to records and archives determined to have long-term value.
When Jett Reno first committed to Starfleet, she padded her resumé by claiming to be a rare and antiquarian bookseller. In reality, Reno had been a smuggler moving hard-to-find folios for a shady antiquarian archivist. (DIS: "Erigah")
Multiple archivists were working at the Bajoran Central Archives in 2375. That year, Ranjen Solbor expressed their concerns to Kai Winn about her study of the so-called "dark texts"; Winn told him to reassure them that "their Kai works for the good of Bajor." (DS9: "The Changing Face of Evil")
In the first draft script of "The Changing Face of Evil", Dukat speculated that, when the Restoration happened, the archivists would be judged, by the Pah-wraiths, as "unworthy." This line of dialogue also referred to the archivists as "librarians".
Archivists such as Hy'Rell ran the Eternal Gallery and Archive. According to the Archive's records, Doctor Marina Derex became an archivist later in life, living out the remainder of her life at the Archive. (DIS: "Labyrinths")