Thomas Dacre, 2nd Baron Dacre of Gilsland, KG (25 November 1467 – 24 October 1525) was the son of Humphrey Dacre, 1st Baron Dacre of Gilsland and Mabel Parr; great-aunt of queen consort Catherine Parr, the sixth and final wife of King Henry VIII of England.
He was born in Cumberland, the eldest of nine children. His father died of natural causes on 30 May 1485 and Thomas succeeded him as Baron Dacre of Gilsland.
Dacre took part in the Battle of Bosworth Field (22 August 1485) on the Yorkist side against Henry Tudor, Earl of Richmond, when Richard III of England was defeated and Richard killed. He however quickly made peace with the victor. This early support for the House of Tudor earned him some favor with Henry VII who would continue to trust his services for the remainder of his reign. Henry VII named him a Knight of the Bath in 1503. He swore loyalty to Henry's son and successor, Henry VIII of England in 1509.
Dacre was named a deputy to the Lord Warden of the Marches (an officer on the border with Scotland) in 1485, and then Warden of the Western marches, and finally Warden-general over all the marches in 1509. Dacre and his forces served under Thomas Howard, Earl of Surrey at the Battle of Flodden (9 September 1513) where the invading army of James IV of Scotland was crushingly defeated and its king killed. Dacre commanded the "Border Lancers" at the battle, and their charge saved Edmund Howard, commander of the English right wing. James IV himself was killed and the Kingdom of Scotland ceased its involvement in the wider War of the League of Cambrai. The victory further helped solidify the reputation of Dacre as a soldier. After the battle, Dacre discovered the body of James IV, informed the Earl of Norfolk, and took it to Berwick upon Tweed. He later wrote that the Scots, "love me worst [i.e. very much; the most] of any Inglisheman living, by reason that I fande the body of the King of Scotts."