Adrian II (also known as Hadrian II), (792–872), pope from 867 to 872, was a member of a noble Roman family, and became pope in 867, at an advanced age.

He maintained, but with less energy, the attitude of his predecessor Nicholas I. Lothar, king of Lorraine, died in 869, leaving Adrian to mediate between the Frankish kings with a view to assuring to the emperor, Louis II, the heritage of the king of Lorraine.

Photius, the Patriarch of Constantinople, shortly after the council in which he had vainly pronounced sentence of deposition against Pope Nicholas I, was driven from the patriarchate by a new emperor, Basil the Macedonian, who favoured his rival Ignatius. An ecumenical council (called by the Latins the 8th Ecumenical Council) was convoked as the Fourth Council of Constantinople to decide this matter. At this council Adrian was represented by legates, who presided at the condemnation of Photius as a heretic, but did not succeed in coming to an understanding with Ignatius on the subject of the jurisdiction over the Bulgarian church .

Like his predecessor Nicholas I, Adrian was forced to submit, in temporal affairs, to the interference of the emperor, Louis II, who placed him under the surveillance of Arsenius , bishop of Orta , his confidential adviser, and Arsenius's son Anastasius, the librarian.

Adrian had married in his youth, and his wife and daughter were still living at his election. They were carried off and assassinated by Anastasius's brother, Eleutherius.

Adrian died in 872 after 5 years as pope.