The Danelaw, as recorded in the Anglo-Saxon Chronicle (also known as the Danelagh; Old English: Dena lagu; Danish: Danelagen), is a historical name given to the part of England in which the laws of the "Danes" held sway and dominated those of the Anglo-Saxons. It is contrasted with "West Saxon law" and "Mercian law". The term has been extended by modern historians to be geographical. The areas that comprised the Danelaw are in northern and eastern England. The origins of the Danelaw arose from the Viking expansion of the 9th century, although the term was not used to describe a geographic area until the 11th century. With the increase in population and productivity in Scandinavia, Viking warriors, having sought treasure and glory in the nearby British Isles, "proceeded to plough and support themselves", in the words of the Anglo-Saxon Chronicle, for the year 876.

Danelaw is also used to describe the set of legal terms and definitions created in the treaties between the English king, Alfred the Great, and the Danish warlord, Guthrum, written following Guthrum's defeat at the Battle of Edington in 878. In 886, the Treaty of Alfred and Guthrum was formalised, defining the boundaries of their kingdoms, with provisions for peaceful relations between the English and the Vikings.

Alfred the Great (Old English: Ælfrēd, Ælfrǣd, "elf counsel"; 849 – 26 October 899) was King of Wessex from 871 to 899.

Alfred successfully defended his kingdom against the Viking attempt at conquest, and by his death had become the dominant ruler in England. He is the only English monarch to be accorded the epithet "the Great". Alfred was the first King of the West Saxons to style himself "King of the Anglo-Saxons". Details of his life are described in a work by the 10th century Welsh scholar and bishop Asser. Alfred was a learned and merciful man who encouraged education and improved his kingdom's legal system and military structure.

Alfred was born in the village of Wanating, now Wantage, Oxfordshire. He was the youngest son of King Æthelwulf of Wessex, by his first wife, Osburh.

In 853, at the age of four, Alfred is said to have been sent to Rome where, according to the Anglo-Saxon Chronicle, he was confirmed by Pope Leo IV who "anointed him as king". Victorian writers interpreted this as an anticipatory coronation in preparation for his ultimate succession to the throne of Wessex. However, his succession could not have been foreseen at the time, as Alfred had three living elder brothers. A letter of Leo IV shows that Alfred was made a "consul"; a misinterpretation of this investiture, deliberate or accidental, could explain later confusion. It may also be based on Alfred's later having accompanied his father on a pilgrimage to Rome where he spent some time at the court of Charles the Bald, King of the Franks, around 854–855.