Eowa (or Eawa) was a son of the Mercian king Pybba and a brother of the Mercian king Penda; according to the Historia Brittonum¹ and the Annales Cambriae,² Eowa was a king of the Mercians himself at the time of the Battle of Maserfield (or Cogwy), in which he was killed, on August 5 of what was probably the year 642 (see note). The later Mercian kings Ethelbald, Offa and Ecgfrith were descended from Eowa; the period of their rule began in 716 following the death of Penda's grandson Ceolred and ended with Ecgfrith's death in December 796.

It was in the battle of Maserfield that Oswald of Northumbria was defeated and killed by the Mercians under Penda. Eowa also died in this battle, although little is known about this. It has been suggested that Eowa may have been a co-ruler of the Mercians alongside Penda, or possibly even superior in status to Penda at this time (if so, this could explain why the Historia Brittonum seems to date Penda's reign from the battle of Maserfield), and that he may have been subject to Oswald and fighting as his ally in the battle.³ The nature of kingship among the Mercians prior to Eowa's death is obscure; it is possible that it was customary for there to be more than one king, and Penda and Eowa may have ruled over the southern and northern Mercians respectively.⁴

Neither Bede, in his Ecclesiastical History of the English People, nor the Anglo-Saxon Chronicle mention Eowa's participation or death at Maserfield, or his previously being a Mercian king, although the Chronicle later mentions him when tracing the descent of Ethelbald and Offa.

In recording the lineage of Eowa's grandson Ethelbald, who ruled from 716 until 757, the Anglo-Saxon Chronicle gives Eowa's ancestors and descendants:

Aethelbald was Alweo's offspring, Alweo Eawa's offspring, Eawa Pybba's offspring...

Later, it gives the lineage of Eowa's great-great-grandson Offa, who ruled from 757 to 796 and was descended from Eowa's son Osmod rather than Eowa's son Alweo. The descent purportedly extends back to Woden:

That Offa was Thingfrith's offspring, Thingfrith Eanwulf's offspring, Eanwulf Osmod's offspring, Osmod Eawa's offspring, Eawa Pybba's offspring, Pybba Creoda's offspring, Creoda Cynewald's offspring, Cynewald Cnebba's offspring, Cnebba Icel's offspring, Icel Eomer's offspring, Eomer Angeltheow's offspring, Angeltheow Offa's offspring, Offa Wermund's offspring, Wermund Wihtlaeg's offspring, Wihtlaeg Woden's offspring.

The Historia Brittonum says that Pybba had 12 sons, but that Penda and Eowa were the ones best known to him.⁵

References

1. Historia Brittonum, (http://www.fordham.edu/halsall/basis/nennius-full.html) Chapter 65: "[Penda] fought the battle of Cocboy, in which fell Eawa, son of Pybba, his brother, king of the Mercians, and Oswald, king of the North-men, and he gained the victory by diabolical agency."
2. Annales Cambriae, (http://www.fordham.edu/halsall/source/annalescambriae.html) 644: "The battle of Cogfry in which Oswald king of the Northmen and Eawa king of the Mercians fell." (The date is given as 644, contrary to both Bede and the Anglo-Saxon Chronicle.)
3. Brooks, Nicholas, "The Formation of the Mercian Kingdom", in S. Bassett, The Origins of Anglo-Saxon Kingdoms (1989), page 166.
4. Kirby, D. P. The Earliest English Kings (1991). Chapter five: "The northern Anglian hegemony in the seventh century". ("The reign of Oswald".)
5. Historia Brittonum, Chapter 60: "This Pubba had twelve sons, of whom two are better known to me than the others, that is Penda and Eawa."