Ambitious noble. Douglas was the son of Sir Archibald Douglas, a Regent of Scotland, who was killed at the Battle of Halidon Hill (1333) and nephew of 'The Good' Sir James Douglas (c.1286 - 1330). He was educated in France, but returned to Scotland in 1348, when he set about recaptured the Douglas lands from the English, which had been lost two years previously following the Battle of Nevill's Cross.
In 1353, he murdered his god-father, another Sir William Douglas, the Lord of Liddesdale (1300-53) who had made a treaty with the English and betrayed Scotland. Douglas gained considerable lands from this uncle and from his father. Encouraged by the French, Douglas raided the England on several occasions and joined the French against the English at the Battle of Poitiers (1356). He took part in the negotiations for the ransom and release of King David II, who had been captured at Nevill's Cross and was created the Earl of Douglas in 1358. In 1363, Douglas took part in a rebellion against David II, but conspired with him and the English the following year to ensure the throne did not fall to his former friend Robert the Steward (1316 - 90), who had served as a Regent in David's minority. However, Douglas was soon reconciled with Robert, who succeeded to the throne as King Robert II in 1371, and Douglas was appointed Justiciar of Scotland.
He acquired the Earldom of Mar, with its associated estates, following the death of his brother-in-law (1374).
His latter years were again spent raiding the English and he died at Douglas (South Lanarkshire). His illegitimate son, George, gave rise to the 'Red Douglases', who became the Earls of Angus, while the Earldom of Douglas passed to his son James (c.1358 - 1388), the 'Black Douglas' line.