Marianus Scotus (1028–1082 or 1083), was an Irish monk and chronicler (who must be distinguished from his namesake Marianus Scotus, d. 1088, abbot of St Peter's, Regensburg), was an Irishman by birth, and called Máel Brigte.
He was educated by a certain Tigernach, and having become a monk in 1052 he crossed over to the continent of Europe in 1056, and his subsequent life was passed in the abbeys of St Martin at Cologne and of Fulda, and at Mainz. He died at Mainz, on December 22, 1082 or 1083 and was buried in Mainz Cathedral.
Marianus wrote a Chronicon, which purports to be a universal history from the creation of the world to 1082. The Chronicon was very popular during the Middle Ages, and in England was extensively used by John of Worcester and other writers. It was first printed at Basel in 1559, and has been edited with an introduction by Georg Waitz for the Monumenta Germaniae historica. Scriptores (Bd. v). See also W. Wattenbach, Deutschlands Geschichtsquellen (Bd. ii., 1894).