Offa (died July 26/29, 796) was the King of Mercia from 757 until his death. Prior to the rise of Wessex in the 9th century, he was arguably the most powerful and successful of the Anglo-Saxon kings, effectively ruling much of Britain south of the River Humber during the latter part of his reign. Offa's Dyke is named after him.

Offa was the son of Thingfrith and a descendant of Eowa, the brother of King Penda, who had ruled over a hundred years before. Following the murder of his cousin King Æthelbald in 757, Offa defeated Beornrad, who fled, thus seizing the throne of Mercia. Offa took over a kingdom that had enjoyed supremacy over southern England during Æthelbald's reign, but this supremacy had been seriously weakened by Æthelbald's death and subsequent internal conflict. Offa thereafter endeavoured to reestablish Mercian power over the other Anglo-Saxon kingdoms.

In Anglo-Saxon England, Stenton argued that Offa was perhaps the greatest king of the English kingdoms, arguing that "no other Anglo-Saxon king ever regarded the world at large with so secular a mind or so acute a political sense". Proof of Offa's abilities was obscured by the lack of a historian (such as Bede a half-century earlier, or Asser a century later) to describe his achievements. However, some care is needed not to regard Offa's reign as just another step towards the formation of England. Offa is best considered in his 8th-century context.



Offa reformed the silver coinage in England, producing the first English silver pennies. Offa's currency reforms were prompted by, and in competition with, those of Charlemagne in Francia, which is reflected in their iconography: they carry a wide range of portraits inspired by Roman coinage and contemporary portrayals of the Biblical King David. Offa's queen, Cynethryth, was the first and only Anglo-Saxon queen ever named or portrayed on the coinage.

The establishment of a new coinage is important evidence for Offa's administrative control over the economy, though there are many difficulties with the chronology and structure of the coinage: a sparse, early coinage was struck at mints in Canterbury, London and somewhere in East Anglia. Two early kings of Kent, Heaberht and Egbert, also struck coins at Canterbury around this time, probably in the 760s and 770s. This early coinage merges into the very large "light coinage", which contains the celebrated portrait coins of Offa and his queen. Coins were also struck at Canterbury in the name of Archbishops Jaenbert and Aethelheard. Around the time of Jaenbert's death and replacement with Aethelheard in 792-3 the silver currency was reformed a second time: in the subsequent "heavy coinage" the weight standard and flan-size were increased, and a standardised non-portrait design was introduced at all three mints.



Along with the silver pennies, a few gold coins were produced, copied from a gold dinar of the Abbasid caliph Al-Mansur dated 157AH (773-4 AD). Offa Rex is centred, though the moneyer clearly had no understanding of Arabic as the Arabic text is upside down. It is likely that the coin was produced in order to trade with Islamic Spain or as part of a yearly donation of alms to the Pope in Rome.

Although Offa had initially used the title "rex Merciorium" (king of the Mercians), he used a multitude of titles over the course of his reign. By the end of his reign, "rex Merciorum" had been settled on as the standard. In 774 however, he is first recorded as using the title "rex Anglorum". Offa was the first king to use that title, and it has been seen as a sweeping statement of his power.

Offa's supposed use of this title has caused considerable debate among scholars. Several of the charters in which Offa is named "rex Anglorum" are of doubtful authenticity. They may represent later forgeries of the 10th century, when this title was standard for kings of England. The evidence of coins strongly suggests, however, that Offa did occasionally use the title "rex Anglorum" as an alternative to "rex Merciorum".