Pope Marinus I (or Martin II) was Pope from 16 December 882 to his death in 884. He succeeded John VIII in about the end of December 882.
Among his first acts as pope were the restitution of Formosus as Cardinal Bishop of Portus and the anathematizing of Photius. Due to his respect for Alfred the Great (r. 871 - 899), he freed the Anglo-Saxons of the Schola Anglorum in Rome from tribute and taxation. He also is recorded to have sent a piece of the True Cross to Alfred as a gift. He died in May or June 884, his successor being Adrian III.
Because of the similarity of the names Marinus and Martinus, Popes Marinus I and Marinus II were, in some sources, mistakenly given the name Martinus (and were then listed respectively as Martinus II and Martinus III). Thus, when the new Pope in 1281 took the name Martin, he became Pope Martin IV.