Constantine II of Scotland in the context of "List of Scottish monarchs"

The Picts were a group of peoples in what is now Scotland north of the Firth of Forth, in the Early Middle Ages. Where they lived and details of their culture can be gleaned from early medieval texts and Pictish stones. The name Picti appears in written records as an exonym from the late third century AD. They are assumed to have been descendants of the Caledonii and other northern Iron Age tribes. Their territory is referred to as "Pictland" by modern historians. Initially made up of several chiefdoms, it came to be dominated by the Pictish kingdom of Fortriu from the seventh century. During this Verturian hegemony, Picti was adopted as an endonym. This lasted around 160 years until the Pictish kingdom merged with that of Dál Riata to form the Kingdom of Alba, ruled by the House of Alpin. The concept of "Pictish kingship" continued for a few decades until it was abandoned during the reign of Caustantín mac Áeda.

Pictish society was typical of many early medieval societies in northern Europe and had parallels with neighbouring groups. Archaeology gives some impression of their culture. Medieval sources report the existence of a Pictish language, and evidence shows that it was an Insular Celtic language related to the Brittonic spoken by the Celtic Britons to the south. Pictish was gradually displaced by Middle Gaelic as part of the wider Gaelicisation from the late ninth century. Much of their history is known from outside sources, including Bede, hagiographies of saints such as that of Columba by Adomnán, and the Irish annals.

Æthelstan or Athelstan (/ˈæθəlstæn/; Old English: Æðelstān [ˈæðelstɑːn]; Old Norse: Aðalsteinn; lit. 'noble stone'; c. 894 – 27 October 939) was King of the Anglo-Saxons from 924 to 927 and King of the English from 927 to his death in 939. He was the son of King Edward the Elder and his first wife, Ecgwynn. Modern historians regard him as the first King of England and one of the "greatest Anglo-Saxon kings". He never married and had no children; he was succeeded by his half-brother, Edmund I.

When Edward died in July 924, Æthelstan was accepted by the Mercians as king. His half-brother Ælfweard may have been recognised as king in Wessex, but died within three weeks of their father's death. Æthelstan encountered resistance in Wessex for several months, and was not crowned until September 925. In 927, he conquered the last remaining Viking kingdom, York, making him the first Anglo-Saxon ruler of the whole of England. In 934, he invaded Scotland and forced Constantine II to submit to him. Æthelstan's rule was resented by the Scots and Vikings, and in 937 they invaded England. Æthelstan defeated them at the Battle of Brunanburh, a victory that gave him great prestige both in the British Isles and on the Continent. After his death in 939, the Vikings seized back control of York, and it was not finally reconquered until 954.

The House of Alpin, also known as the Alpinid dynasty, Clann Chináeda, and Clann Chinaeda meic Ailpín, was the kin-group which ruled in Pictland, possibly Dál Riata, and then the kingdom of Alba from Constantine II (Causantín mac Áeda) in the 940s until the death of Malcolm II (Máel Coluim mac Cináeda) in 1034.

Kings traced their descent from Kenneth MacAlpin (and not from his father, Alpín mac Echdach), and Irish genealogies in the Book of Ballymote and the Book of Lecan refer to the kindred as Clann Cináeda meic Ailpín by prioritising descent from Kenneth.

The Battle of Brunanburh was fought in 937 between Æthelstan, King of England, and an alliance of Olaf Guthfrithson, King of Dublin; Constantine II, King of Scotland; and Owain, King of Strathclyde. The battle is sometimes cited as the point of origin for English national identity: historians such as Michael Livingston argue that "the men who fought and died on that field forged a political map of the future that remains, arguably making the Battle of Brunanburh one of the most significant battles in the long history not just of England, but of the whole of the British Isles."

Following an unchallenged invasion of Scotland by Æthelstan in 934, possibly launched because Constantine had violated a peace treaty, it became apparent that Æthelstan could be defeated only by an alliance of his enemies. Olaf led Constantine and Owen in the alliance. In August 937 Olaf and his army sailed from Dublin to join forces with Constantine and Owen, but they were routed in the battle against Æthelstan. The poem "Battle of Brunanburh" in the Anglo-Saxon Chronicle recounts that there were "never yet as many people killed before this with sword's edge ... since the east Angles and Saxons came up over the broad sea".

Olaf Guthfrithson or Anlaf Guthfrithson (Old Norse: Óláfr Guðrøðsson [ˈoːˌlɑːvz̠ ˈɡuðˌrøðsˌson]; Old English: Ánláf; Old Irish: Amlaíb mac Gofraid; died 941) was a Hiberno-Scandinavian (Irish-Viking) leader who ruled Dublin and Viking Northumbria in the 10th century. He was the son of Gofraid ua Ímair and great-grandson of Ímar, making him one of the Uí Ímair. Olaf succeeded his father as King of Dublin in 934 and succeeded in establishing dominance over the Vikings of Limerick when he captured their king, Amlaíb Cenncairech, in 937. That same year he allied with Constantine II of Scotland in an attempt to reclaim the Kingdom of Northumbria which his father had ruled briefly in 927. The forces of Olaf and Constantine were defeated by the English led by Æthelstan at the Battle of Brunanburh in 937.

Olaf returned to Ireland in 938 but after Æthelstan's death the following year Olaf left for York where he was quickly able to establish himself as king, with his brother Blácaire mac Gofraid being left to rule in Dublin. Olaf and Æthelstan's successor Edmund met in 939 at Leicester where they came to an agreement regarding the division of England between them. This agreement proved short-lived, however, and within a few years Vikings had occupied the Five Boroughs of Derby, Leicester, Lincoln, Nottingham and Stamford. Olaf died in 941 and was succeeded in Northumbria by his cousin Olaf Cuaran. At the time of his death, the Irish annals title him "king of Danes" and "king of the Fair Foreigners and the Dark Foreigners".

Máel Coluim mac Domnaill (anglicised Malcolm I; 5 October 897 – 954) was king of Alba (before 943–954), becoming king when his cousin Constantine II abdicated to become a monk. He was the son of Donald II.