noted Highland outlaw whose reputation as a Scottish Robin Hood was exaggerated in Sir Walter Scott's novel Rob Roy (1818) and in some passages in the poems of William Wordsworth. He frequently signed himself Rob Roy (“Red Rob”), in reference to his dark red hair.

Rob's father, Donald MacGregor, a younger brother of the chief of the clan MacGregor, received a military commission from the deposed King James II after the Glorious Revolution (1688–89). Rob was a freebooter with uncertain loyalty to James and was probably also engaged in cattle stealing and blackmail, old and at that time still honourable Highland practices. When the penal laws against the MacGregors were reintroduced in 1693, Rob took the name of Campbell. Since his lands lay between those of the rival houses of Argyll and Montrose, for a time he was able to play one off against the other to his own advantage. James Graham, 1st duke of Montrose, succeeded in entangling him in debt, and by 1712 Rob was ruined.

Rob then embarked on a career of brigandage, chiefly at the expense of Montrose. During the Jacobite (pro-Stuart) rebellion of 1715 he was distrusted by both sides and plundered each impartially. After the rebellion was put down he was treated leniently because of the intercession of John Campbell, 2nd duke of Argyll (Argyll, John Campbell, 2nd Duke of, Duke Of Greenwich, Marquess Of Kintyre And Lorne, Earl Of Campbell And Cowall, Earl Of Greenwich, Viscount Of Lochow And Glenyla, Baron Of Chatham, Lord Of). Rob continued his exploits against Montrose until 1722, when Argyll brought about a reconciliation. Later, however, Rob was arrested and confined in Newgate Prison, London; he was pardoned in 1727 when about to be transported to Barbados.

In his old age Rob became a Roman Catholic. His letters show that he was well educated; the view of him as a mere brutish highwayman seems not to do him justice.