Æthelred II, known as Æthelred the Unready, was King of the English from 978 to 1013 and again from 1014 until his death in 1016. His epithet comes from the Old English word unræd meaning "poorly advised"; it is a pun on his name, which means "well advised".

Æthelred was the son of King Edgar and Queen Ælfthryth. He came to the throne at about the age of 12, following the assassination of his elder half-brother, King Edward the Martyr.

The chief characteristic of Æthelred's reign was conflict with the Danes. After several decades of relative peace, Danish raids on English territory began again in earnest in the 980s, becoming markedly more serious in the early 990s. Following the Battle of Maldon in 991, 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 1013, King Sweyn Forkbeard of Denmark invaded England, as a result of which Æthelred fled to Normandy in 1013 and was replaced by Sweyn. After Sweyn died in 1014, Æthelred returned to the throne, but he died just two years later. Æthelred's 37-year combined reign was the longest of any Anglo-Saxon English king and was only surpassed in the 13th century, by Henry III. Æthelred was briefly succeeded by his son Edmund Ironside, but Edmund died after a few months and was replaced by Sweyn's son Cnut. Another of Æthelred's sons, Edward the Confessor, would become king of England in 1042.
Name

Æthelred's first name, composed of the elements æðele 'noble', and ræd 'counsel', is typical of the compound names of those who belonged to the royal House of Wessex, and it characteristically alliterates with the names of his ancestors, like Æthelwulf 'noble-wolf', Ælfred 'elf-counsel', Eadweard 'rich-protection', and Eadgar 'rich-spear'.

Æthelred's notorious nickname, Old English Unræd, is commonly translated into present-day English as "The Unready" (less commonly but more accurately "The Redeless"). The Anglo-Saxon noun unræd means "evil counsel", "bad plan", or "folly". It was most often used in reference to decisions and deeds, but once in reference to the ill-advised disobedience of Adam and Eve. The element ræd in unræd is the same element in Æthelred's name that means 'counsel' (compare the cognate in the German word Rat and Dutch raad). Thus Æþelræd Unræd is an oxymoron: "Noble counsel, No counsel". The nickname has also been translated as "ill-advised", "ill-prepared", thus "Æthelred the ill-advised".

Because the nickname was first recorded in the 1180s, more than 150 years after Æthelred's death, it is doubtful that it carries any implications as to the reputation of the king in the eyes of his contemporaries or near contemporaries.