The Battle of Flodden or Flodden Field was a battle between the Kingdom of England and the Kingdom of Scotland. The battle was fought in the county of Northumberland in northern England on 9 September 1513, between an invading Scots army under King James IV and an English army commanded by the Earl of Surrey. It was part Part of the War of the League of Cambrai and an English victory. In terms of troop numbers, it was the largest battle fought between the two Kingdoms. James IV was killed in the battle, becoming the last monarch from the British Isles to suffer such a death to date.

This conflict began when James IV, King of Scots declared war on England to honour the Auld Alliance with France by diverting Henry VIII's English troops from their campaign against the French king Louis XII. Henry VIII had also opened old wounds by claiming to be the overlord of Scotland which angered the Scots and the King. At this time England was involved in the War of the League of Cambrai—defending Italy and the Pope from the French a member of the "Catholic League". Pope Leo X, already a signatory to the anti-French treaty of Mechlin, sent a letter to James threatening him with ecclesiastical censure for breaking his peace treaties with England on 28 June 1513, and subsequently James was excommunicated by Cardinal Christopher Bainbridge. James also summoned sailors and sent the Scottish navy, including the Great Michael to join the ships of Louis XII of France. Henry was in France with the Emperor Maximilian at the siege of Thérouanne. The Scottish Lyon King of Arms brought James IV's letter of 26 July to him. James asked him to desist from attacking France in breach of their treaty, Henry replied on 12 August that James was mistaken and resistance to any of his attempts on England would be in place. Using the pretext of revenge for the murder of Robert Kerr, a Warden of the Scottish East March who had been killed by John "The Bastard" Heron in 1508, James invaded England with an army of about 30,000 men in 1513.

Surrey's army lost 1,500 men killed. There were various conflicting accounts of the Scottish loss. A contemporary French source, the Gazette of the Battle of Flodden, said that about 10,000 Scots were killed, a claim made by Henry VIII on 16 September while he was still uncertain of the death of James IV. William Knight sent the news from Lille to Rome on 20 September, claiming 12,000 Scots had died with less than 500 English casualties. Italian newsletters put the Scottish losses at 18 or 20 thousand and the English at 5000. Brian Tuke, the English Clerk of the Signet, sent a newsletter stating 10,000 Scots killed and 10,000 escaped the field. Tuke reckoned the total Scottish invasion force to have been 60,000 and the English army at 40,000. George Buchanan wrote in his History of Scotland that, according to the lists that were compiled throughout the counties of Scotland, there were about 5,000 killed. A plaque on the monument to the 2nd Duke of Norfolk (as the Earl of Surrey became in 1514) at Thetford put the figure at 17,000..