Cenelm was a son of King Coenwulf of Mercia who, according to some sources, reigned as a seven-year-old child for a few months after his father's death in 821, but was murdered. However, Cenelm was also mentioned in charters from years before, which would be incompatible with an age of seven in 821, and is generally believed to have died before his father, in 812. He would have been the sixteenth king of Mercia.
Mercia was one of the pre-Conquest Anglo-Saxon kingdoms of England.
Its centre was in the valley of the River Trent, and its tributaries, but later it grew to extend from the Humber to the Thames, and west to the borders of Wales.
Later, in 853, the kingdoms allied to "conquer" North Wales, and the Mercian king married the daughter of Ethelwulf, King of the West Saxons.
Mercia was one of the kingdoms of the Anglo-Saxon Heptarchy, in what is now England, in the region of the Midlands.
Mercia soon returned to the rule of her own king but its days as the leading power of England had passed.
The Danes drove Burgred, the last king of Mercia from his kingdom in 874 and in 886, the eastern part of the kingdom became part of the Danelaw, while the western portion was occupied by Wessex.