In the Battle of Vimeiro on 21 August 1808, the British under General Arthur Wellesley (who later became the Duke of Wellington) defeated the French under Major-General Jean-Andoche Junot near the village of Vimeiro, near Lisbon, Portugal during the Peninsular War. This battle put an end to the first French invasion of Portugal.

Four days after the Battle of Roliça, Wellesley's army was attacked by a French army under General Junot near the village of Vimeiro. The battle began as a battle of manoeuvre, with French troops attempting to outflank the British left, but Wellesley was able to redeploy his army to face the assault. Meanwhile, Junot sent in two central columns but these were forced back by sustained volleys from troops in line. Soon afterwards, the flanking attack was beaten off and Junot retreated towards Torres Vedras, having lost 2,000 men and 13 cannon, compared to 700 Anglo-Portuguese losses. No pursuit was attempted because Wellesley was superseded by Sir Harry Burrard and then Sir Hew Dalrymple (one having arrived during the battle, the second soon after).

After the French defeat, Dalrymple gave the French more generous terms than they could have hoped for. Under the terms of the Convention of Sintra, the defeated army was transported back to France by the British navy, complete with its loot, guns and equipment. The Convention of Sintra caused an outcry in Britain. An official enquiry exonerated all three men but both the military establishment and public opinion blamed Dalrymple and Burrard. Both men were given administrative posts and neither had a field command again. Wellesley, who had bitterly opposed the agreement, was returned to active command in Spain and Portugal.