King of Mercia, succeeded to the throne in 796, on the death of Ecgfrith, son of Offa. His succession is somewhat remarkable, as his direct ancestors do not seem to have held the throne for six generations. In 798 he invaded Kent, deposed and imprisoned Eadberht Præn, and made his own brother Cuthred king. Cuthred reigned in Kent from 798 to 807, when he died, and Cnwulf seems to have taken Kent into his own hands. It was during this reign that the archbishopric of Lichfield was abolished, probably before 803, as the Hygeberht who signed as an abbot at the council of Cloveshoe in that year was presumably the former archbishop. Cnwulf appears from the charters to have quarrelled with Wulfred of Canterbury, who was consecrated in 806, and the dispute continued for several years. It was probably only settled at Cloveshoe in 825, when the lawsuit of Cwnthryth, daughter and heiress of Cnwulf, with Wulfred was terminated. Cnwulf may have instigated the raid of Æthelmund, earl of the Hwicce, upon the accession of Ecgberht. He died in 821, and was succeeded by his brother Ceolwulf I.
See Earle and Plummers edition of the Anglo-Saxon Chronicle, 796, 819 (Oxford, 1892); W. de G. Birch, Cartularium Saxonicum, 378 (London, 18851893).