Titles:
King of Dalriada ( 841 - 844)
King of the Picts ( 844) as Kenneth III
King of Scots ( 844 - 859)

Kenneth I the Hardy (c. 810 – 858; Kenneth mac Alpin) succeeded his father, Alpin II, to the throne of Dalriada. He soon obtained the Pictish throne in 843 and became the first king to rule the Picts of Pictavia and the Scots of Dalriada. It is possible that intermarriage with the Picts helped secure Kenneth's throne. The joint kingdom was known as Alba from the Gaelic name for the area. He was the first king of the House of Alpin.

Recalling the peculiarity of a matrilineal succession which governed Pictish crowns, it is evident that Kenneth Mac Alpin grounded his claims to the Pictish crown from his mother's bloodlines. The brutalizing defeat at the hands of the Vikings in 839 killed most of the Pictish nobility, including the King of Picts and Scots Uven Mac Angus II, his brother Bran, and "numberless others". This opened Mac Alpin's claim to the vacant Pictish throne (via his mother who was a Pictish princess). The Pictish kingdoms had been severely weakened by attacks from the Vikings and were in no condition to dispute his claim.

His claim to the crown of Dalriada came from his father, who was a member of clan Gabhran, which had produced most Scottish kings, such as his ancestors King Eachaidh, King Alpin Mac Eachaidh, King Aed, and King Fergus. His Pictish mother was descended from the royal house of Fortrenn, and his great-grand uncle, Alpin Mac Eachaidh had actually reigned as King of Picts until deposed by Oengus I. It is thus that Kenneth Mac Alpin was one of several nobles with a claim to the crown of Picts and Scots.

By the year 843, he had created a semblance of unity among the warring societies of the Picts, Scots, Britons, and Angles after he had defeated the Picts in battle. MacAlpin created his capital at Forteviot, also called Scone, in Pictish territory. He then moved his religious center to Dunkeld on the River Tay in present-day Perthshire, to where he transferred the remains of St. Columba from the Isle of Iona.

At roughly the same time that the people of Wales were separated from the invading Saxons by the artificial boundary of Offa's Dyke, MacAlpin was creating a kingdom of Scotland. MacAlpin's successes in part were due to the threat coming from the raids of the Vikings, many of whom became settlers. The seizure of control over all Norway in 872 by Harald Fairhair caused many of the previously independent Jarls to look for new lands to establish themselves.

One result of the coming of the Norsemen and Danes, with their command of the sea, was that the kingdom of Scotland became surrounded and isolated. The old link with Ireland was broken, the country was now cut off from southern England and the Continent, thus, the kingdom of Alba established by MacAlpin was thrown in upon itself and united against a common foe. According to the Huntingdon Chronicle, he "was the first of the Scots to obtain the monarchy of the whole of Albania, which is now called Scotia."

Kenneth is thought to have died of a tumor after reigning for sixteen years. He died at Forteviot in 858 and was buried on the Isle of Iona. His brother, Donald I, succeeded him, as was the custom.

Throughout this whole period, the dominion of the Scottish kings was essentially limited to Fortrenn, the Mearns and Dalriada, as the rest of the Pictish lands were under the yoke of the Vikings. Nonetheless, within a few generations, the Pictish language is forgotten, the Pictish Church taken over by the Scottish Columban Church and most vestiges of Pictish culture assimilated.

Furthermore, the seat of Kings is eventually moved to Scone, sacred heart of the Pictish land, and the sons of Mac Alpin accept the crown over the land of Picts and Scots seated on a slab of stone (the Stone of Scone) which Scottish myth tells us was carried by the Celtic tribes since their origins in Spain, brought to Tara in Ireland, built into the wall of Dunstaffnage Castle and then brought to Scone.