John Stuart, second duke of Albany (c.1481/4-1536) was a Scottish nobleman who served Francis I of France during the war that ended in disaster at Pavia in 1525.
Albany was the son of Alexander Stuart, first duke of Albany (in the second creation) and Anne de La Tour. His father died in 1485, having lost his titles in 1483. His young son was raised in France by his mother. In 1513 James IV of Scotland was killed at the battle of Flodden, and was succeeded by the infant James V. At first the new king's mother Margaret Tudor served as regent, but in 1515 the Scottish Parliament asked Albany, who was then third in line to the throne, to return home to serve as Protector of Scotland. In July 1515 he became Regent of Scotland, and in August he arrested Margaret at Stirling. Albany was closely related to the young king, and on 13 November 1516 was even declared heir to the throne.
Albany was a pro-French and anti-English regent. In 1517 he visited France where he agreed the Treaty of Rouen, renewing the alliance between France and Scotland. He returned to Scotland in 1521, when he was reconciled with Margaret (to the extent that his enemies accused him of planning to marry her).
During the First Hapsburg-Valois War (1521-25) England became involved in the fighting, campaigning ineffectively in northern France in 1522-23. Albany responded by attempting to organise an invasion of England in September 1522. This campaign failed, after Albany missed a chance to attack a defenceless Carlisle and Albany briefly travelled to France. He returned to Scotland in 1523 and led a second, equally unsuccessful campaign in September 1523. This time he did get as far as Wark Castle, beginning a siege on 1 November 1524, but this was abandoned soon afterwards when an English relief army approached.
In May 1524 Albany returned to France where he entered the service of Francis I (he was officially removed as Regent of Scotland later in 1524, after failing to meet an August deadline for a return to Scotland). In October he accompanied Francis on one of his many invasions of Italy. Francis had formed an alliance with Pope Clement VII, in which he agreed to send an army south to invade Naples. In December Albany was given command of this army of 11,000 men and sent south. This meant that he missed the disastrous French defeat at Pavia (24 February 1525), at which Francis was captured. Unsurprisingly Albany's army fell apart when the new reached them, and the duke had to escape back to France by sea.
After that he served Francis as a diplomat. In 1530 he was appointed Ambassador to Rome and in 1533 he brought Catherine de Medici (who was his wife's niece) to France, where she married Francis's eldest son Henry (this would be a fateful marriage - after the death of his older brother Henry would ascend the throne as Henry II and Catherine would become a dominant figure during the early stages of the French Wars of Religion). Albany died on 2 June 1536 with no legitimate heir.