The 51st (2nd Yorkshire West Riding) Regiment of Foot was a British Army line infantry regiment. During the Childers Reforms it was united with the 105th Regiment of Foot (Madras Light Infantry) to form the King's Own Yorkshire Light Infantry.
The 51st was formed in 1755 for service during the Seven Years' War. Originally numbered the 53rd, Napiers, Regiment of Foot, and bearing the name of its colonel, Robert Napier, it was re-numbered in 1757, with the name of its new colonel, as 51st Brudenells Regiment. In 1759 they saw action at the battle of Minden, which later became their first battle honour. Following the war, the 51st had garrison duty in Ireland and Minorca, acquiring their county association in 1783 as the 51st (2nd Yorkshire West Riding) Regiment.
The regiment was at Gibraltar at the start of the French Revolutionary Wars and in 1795 they were in Corsica at the siege of Calvi.
In 1803-05 it took part in the Kandyan Wars in Sri Lanka.
In 1808 the 51st became a Light Infantry regiment and took part in Peninsular War, where they fought in every major action. Following Napoleon's escape from Elba in 1815, they fought in the Battle of Waterloo.
In 1881, as part of the Childers Reforms, the 51st was amalgamated with the 105th Regiment of Foot (Madras Light Infantry) to form the King's Own Yorkshire Light Infantry.