Ceolwulf II (died c. 879) was the last king of independent Mercia. He succeeded Burgred of Mercia who was deposed by the Vikings in 874. His reign is generally dated 874 to 879 based on a Mercian regnal list which gives him a reign of five years. However, D. P. Kirby argues that he probably reigned into the early 880s. By 883, he had been replaced by Æthelred, Lord of the Mercians, who became ruler of Mercia under the lordship of Alfred the Great, king of Wessex.
On anthroponymic grounds, Ceolwulf is thought to belong to the C dynasty of Mercian kings, a family which claimed descent from Pybba of Mercia. The C dynasty, beginning with Coenwulf, may have had ties to the ruling family of Hwicce in south-west Mercia.
Ceolwulf's immediate ancestry is unknown, but he is thought to be a descendant of Ceolwulf I through his daughter Ælfflæd. Ælfflæd was first married to Wigmund, son of King Wiglaf, and then to Beorhtfrith, son of King Beorhtwulf. Far from being "an unwise king's thane", it is clear that Ceolwulf was a descendant of previous kings. A number of thegns who witnessed charters under Burgred witnessed charters under Ceolwulf, and his charters were witnessed by Mercian bishops, testifying to his acceptance in Mercia.
The Anglo-Saxon Chronicle offers the following account of Ceolwulf:
This year went the army [i.e. the Great Heathen Army] from the Kingdom of Lindsey to Repton, and there took up their winter-quarters, drove the king [i.e. of Mercia], Burgred, over sea, when he had reigned about two and twenty winters, and subdued all that land. He then went to Rome, and there remained to the end of his life. And his body lies in the church of Sancta Maria, in the school of the English nation. And the same year they gave Ceolwulf, an unwise king's thane, the Mercian kingdom to hold; and he swore oaths to them, and gave hostages, that it should be ready for them on whatever day they would have it; and he would be ready with himself, and with all those that would remain with him, at the service of the army.