The title Earl of Morton was created in the Peerage of Scotland in 1458 for James Douglas. Along with it, the title Lord Aberdour was granted. This latter title is the courtesy title for the eldest son and heir to the Earl of Morton.

The 1st Earl of Morton succeeded to the title 3rd Lord Dalkeith from his father, a title held by the Earls of Morton as subsidiary until the 7th earl, who sold it with its estates to the Buccleuch family. It was the courtesy title for the eldest son and heir until then.

While the earldom was attainted between 1581 and 1586, the nephew-in-law of the 4th earl (also grandson of the 3rd earl), John Maxwell, 7th Lord Maxwell called himself "5th Earl of Morton". Lord Maxwell's title of Morton, which had been revoked in 1585, was revived in 1587 and 1592, so that both men, Lord Maxwell and the 6th Earl of Morton, were in possession, and a conflict arose; and though - at the time of the 7th Earl of Morton - John, 8th Lord Maxwell (c. 1586-1613), also claimed the earldom, he was attainted in 1609 and his rights then failed, his titles and estates being restored in 1618 to his brother Robert, with the title of earl of Nithsdale (1620) in lieu of Morton.

Earls of Morton (1458)

• James Douglas, 1st Earl of Morton (d. 1493)
• John Douglas, 2nd Earl of Morton (d. 1513)
• James Douglas, 3rd Earl of Morton (d. 1548) ("abeyant" 1548)
• James Douglas, 4th Earl of Morton (c. 1516-1581) (abeyance terminated 1550, attainted 1580/81)
• Archibald Douglas, 5th Earl of Morton (c. 1555-1588), also 8th Earl of Angus (attainder reversed 1586)
• William Douglas, 6th Earl of Morton (1540-1606)
• William Douglas, 7th Earl of Morton (1582-1648)
• Robert Douglas, 8th Earl of Morton (d. 1649)
• William Douglas, 9th Earl of Morton (d. 1681)
• James Douglas, 10th Earl of Morton (d. 1686)
• James Douglas, 11th Earl of Morton (d. 1715)
• Robert Douglas, 12th Earl of Morton (d. 1730)
• George Douglas, 13th Earl of Morton (1662-1738)
• James Douglas, 14th Earl of Morton (c. 1703-1768)
• Sholto Charles Douglas, 15th Earl of Morton (1732-1774)
• George Douglas, 16th Earl of Morton (1761-1827)
• George Sholto Douglas, 17th Earl of Morton (1789-1858)
• Sholto John Douglas, 18th Earl of Morton (1818-1884)
• Sholto George Douglas, 19th Earl of Morton (1844-1935)
• Sholto Charles John Hay Douglas, 20th Earl of Morton (1907-1976)
• John Charles Sholto Douglas, 21st Earl of Morton (b. 1927)

Heir Apparent: his son John Stewart Sholto Douglas, Lord Aberdour (b. 17 January 1952)