English king Æthelred II orders the killing of all Danes in England, known today as the St. Brice's Day massacre.

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".

The Danes were a North Germanic tribe inhabiting southern Scandinavia, including the area now comprising Denmark proper, northern and eastern England, and the Scanian provinces of modern-day southern Sweden, during the Nordic Iron Age and the Viking Age. They founded what became the Kingdom of Denmark. The name of their realm is believed to mean "Danish March", viz. "the march of the Danes", in Old Norse, referring to their southern border zone between the Eider and Schlei rivers, known as the Danevirke.

The St. Brice's Day massacre was a mass killing of Danes within England on 13 November 1002, on the order of King Æthelred the Unready of England. The Anglo-Saxon chronicle relates that the massacre was carried out in response to an accusation that the Danes would "beshrew [Æthelred] of his life, and afterwards all his council, and then have his kingdom without any resistance." King Æthelred thus ordered the killing of many Danes within his territory. The retaliation by the Danish King Sweyn Forkbeard over the next few years would earn Æthelred the nickname Æthelred the Ill-Advised.

November 13 is the 317th day of the year in the Gregorian calendar; 48 days remain until the end of the year.