Æthelred the Unready, or Æthelred II (Old English: Æþelræd, c. 968 – 23 April 1016) was King of the English (978–1013 and 1014–1016). He was the son of King Edgar the Peaceful and Queen Ælfthryth and was between ten and thirteen years old when his half-brother Edward the Martyr was murdered on 18 March 978. Although Æthelred was not personally suspected of participation, the murder was committed at Corfe Castle by his attendants, making it more difficult for the new king to rally the nation against the military raids by Danes, especially as the legend of St Edward the Martyr grew.
From 991 onwards, Æthelred paid tribute, or Danegeld, to the Danish king. In 1002, Æthelred ordered what became known as the St. Brice's Day massacre of Danish settlers. In 1003, King Sweyn Forkbeard of Denmark invaded England, as a result of which Æthelred fled to Normandy in 1013 and was replaced by Sweyn. He would return as king, however, after Sweyn's death in 1014.
"Unready" is a mistranslation of the Old English word unræd (meaning bad-counselled, the ræd being cognate with Rat in German), a twist on his name "Æthelred", meaning noble-counseled. It should not be "unprepared", but rather "ill-advised".