The English Civil War battle of Roundway Down was fought on July 13, 1643, at the eponymous hill just north of Devizes in Wiltshire. Lord Henry Wilmot, Earl of Rochester, commanding the Royalist forces, won a crushing victory over the Parliamentarian Sir William Waller.
Lord Ralph Hopton's army had previously drawn with Waller at Lansdowne, but was weakened and moved to Devizes, which Waller besieged with his artillery. However, the arrival of cavalry reinforcements from Oxford, led by Prince Maurice (nephew of King Charles I), forced Waller to draw off from the siege and prepare for a battle.
Maurice and Wilmot charged, with partial success, Waller's cavalry fleeing before them, but the infantry held its ground. Hopton, however, saw the opportunity and sallied forth from Devizes to attack in the rear. The Parliamentary line melted away, losing more than a thousand men killed or captured.
This was effectively the end of Parliamentary support in the West country; Prince Rupert entered Bristol on July 25.