Sir Thomas Erpingham KG (c. 1355–1428) was an English knight who became famous as the commander of King Henry V's longbow wielding archers at the Battle of Agincourt. He was immortalised as a character in the play Henry V by William Shakespeare. It is, however, his lengthy and loyal service to John of Gaunt, Henry IV and Henry V, which contributed significantly to the establishment of the House of Lancaster upon the English throne, that is his true legacy.