Ammĭānus Marcellīnus, i, m., a Latin historian of the 4th century. Of his work, Rerum gestarum libri XXXI., which extended from the beginning of the reign of Nerva (91 A.D.) to the death of Valens (378), the first thirteen books are lost; cf., concerning him, Bähr. Lit. Gesch. 349 sq., and Teuffel, Rom. Lit. § 421, 1-5.