The Battle of Bosworth Field (or the Battle of Bosworth) was the penultimate battle of the Wars of the Roses, the civil war between the House of Lancaster and the House of York that raged across England in the latter half of the 15th century. Fought on 22 August 1485, the battle was won by the Lancastrians. Their leader Henry Tudor, Earl of Richmond, became the first English monarch of the Tudor dynasty by his victory and subsequent marriage to a Yorkist princess. His opponent Richard III, the last king of the House of York, was killed in the battle. Historians consider Bosworth Field to mark the end of the Plantagenet dynasty, making it one of the defining moments of English history.

Richard's reign began in 1483 when he seized the throne from his twelve-year-old nephew Edward V. The boy and his younger brother soon disappeared, to the distress of many, and Richard's support was further eroded by rumours of his involvement in the death of his wife. Across the English Channel Henry Tudor, a descendant of the greatly diminished House of Lancaster, seized on Richard's difficulties and laid claim to the throne. Henry's first attempt to invade England in 1483 was frustrated by a storm, but his second arrived unopposed on 1 August 1485 on the southwest coast of Wales. Marching inland, Henry gathered support as he made for London. Richard hurriedly mustered his troops and intercepted Henry's army south of the town of Market Bosworth in Leicestershire. Lord Thomas Stanley and Sir William Stanley also brought a force to the battlefield, but held back while they decided which side it would be more advantageous to support.