Indulf was king of Scotland from 954 to 962. He was the son of King Constantine II, second cousin of the previous king Malcolm I, and second cousin first removed of his successor Dubh. He became king in 954, but there is no record of his coronation, if there ever was one.

During his reign, a rebirth of Danish invasions began. These visits, which were growing more familiar but not more welcome, came to brace the patriotism of the nation when in danger of becoming relaxes. The Norsemen crossed the sea in a fleet of fifty ships. They ravaged the southern shores of England. Intent, however on gathering more booty before returning to their own country, they sailed northward and entered the Firth of Forth. Their appearance spread terror along both shores of the Firth. The timid left their houses and fled. The courageous hastened to the beach, and mustered in such force that the Danes deemed it prudent to withdraw. Dropping down the Firth past the May, their galleys crept round the "neuk" of Fife and entered the estuary of the Tay. Again a phalanx of determined combatants lined the shores of the river and the invaders saw that there was no safe landing place. They sailed away, and coasting along the shores of Angus and Mearns, they arrived off Buchan, searching all the way for an unguarded creek or bay into which they might run their galleys and let loose their ravaging hordes like a flock of vultures upon the land. The coast bristled with defenders ready to grapple with the foe should he dare to land and throw him back into the waves. The invaders put their helms about and bore away to the Danish shore. It was a feint. After vanishing in the blue, they suddenly reappeared. Finding the coast unguarded, they landed unopposed in Banffshire near Cullen. Brief time was given them to pillage and slay. Indulf soon came up with them and the two armies were installed in combat. The Danes were worsted and driven to their ships and hoisting sail, this time in earnest, they made off to their own country.

Indulf left one lasting contribution. His father, Constantine II, fleeing before Athelstan, had abandoned the Lothian, and with the Lothians a city destined one day to be the capital of Scotland, to the English. In a decisive victory over Edwin of Deira, Indulf recaptured the fortress in Edinburgh, Dun Eden.

Indulf married at some point in his life, but the details are scanty. The date and place of the marriage are unrecorded, and the name of his wife is similarly unknown. He had three sons, all of whom later died violently in separate engagements.

Like his father before him, Indulf at least intended to abdicate and become a monk. Conflicting accounts state that he was killed by invading Vikings in 962 at the Battle of the Bauds in Findochty, Banffshire. It is unclear whether at the time he was still king or if he had already abdicated.

His son, Culen, later became king in 966.