Thomas Boyd, Earl of Arran (died c. 1473) was a Scottish nobleman.
Thomas was the son of Robert, 1st Lord Boyd, who was a regent during the minority of James III. His father was able to have Thomas created Earl of Arran and Baron Kilmarnock in the Peerage of Scotland and arrange Thomas' marriage to Princess Mary, sister of James III in 1467. The marriage was unpopular, especially after the Boyds were convicted of treason for abducting James and Mary and establishing the regency.
While Robert and Thomas Boyd were out of the country negotiating the cession of Orkney to Scotland and the king's marriage to Margaret of Denmark, the regency was overthrown, and they were attainted for high treason in 1469. However, Thomas fulfilled his mission, that of bringing the king's bride, Margaret, to Scotland, and then, warned by his wife, escaped to the continent of Europe. He is mentioned very eulogistically in one of the Paston Letters, but practically nothing is known of his subsequent history. He probably died at Antwerp between 1471 and 1473.
Thomas Boyd was contracted, 20 January 1465, to Marion, youngest daughter of Gilbert, 1st Lord Kennedy, but this marriage does not appear to have taken place. After his first marriage to Lady Elizabeth Montgomerie, daughter of Alexander Montgomerie, 1st Lord Montgomerie and before 26 April 1467, he married the Princess Mary, eldest daughter of King James II of Scotland. When she returned to Scotland is not known, but as she is said to have been greatly attached to her husband it is supposed that she returned in hopes of obtaining a pardon from her brother. She was, however, confined at Kilmarnock, and the Earl, her husband, summoned to appear within sixty days, which he failing to do, his marriage with the King's sister was declared null and void, and she was compelled to marry James, Lord Hamilton.