The son of King Duncan I (reigned 1034–40), Malcolm lived in exile in England during part of the reign of his father's murderer, Macbeth (reigned 1040–57). Malcolm killed Macbeth in battle in 1057 and then ascended the throne. After the conquest of England by William the Conqueror, in 1066, Malcolm gave refuge to the Anglo-Saxon prince Edgar the Aetheling and his sisters, one of whom, Margaret (later St. Margaret), became his second wife.

Malcolm acknowledged the overlordship of William in 1072 but nevertheless soon violated his feudal obligations and made five raids into England. During the last of these invasions he was killed by the forces of King William II Rufus (reigned 1087–1100). Except for a brief interval after Malcolm's death, the Scottish throne remained in his family until the death of Queen Margaret, the Maid of Norway, in 1290. Of Malcolm's six sons by Margaret, three succeeded to the throne: Edgar (reigned 1097–1107), Alexander I (1107–24), and David I (1124–53).