Lieutenant-General Sir John William Waters KCB (1774 – 21 November 1842) was a Welsh officer in the British Army during the Napoleonic Wars.

Waters joined the army in 1797; in 1805, was promoted captain, and in 1808, aide-de-camp to Brigadier Charles William Stewart (afterwards 3rd Marquis of Londonderry), after which he went to Portugal.

He had become lieutenant on 15 February 1799, and in reward for his conduct during the mutiny at Gibraltar in 1802 the Prince Edward, Duke of Kent obtained a company for him in the York Rangers on 24 September 1803.

[2] In August 1808, owing to the Duke of Kent's recommendation, he was made aide-de-camp to Brigadier Charles William Stewart (afterwards third Marquis of Londonderry).

Waters was promoted major on 16 February 1809, and was attached to the Portuguese army (with the local rank of lieutenant-colonel), but employed on intelligence duties.

Wellington wrote of him on 26 October, when he was going home for a time with Stewart: He has made himself extremely useful to the British army by his knowledge of the languages of Spain and Portugal, by his intelligence and activity.

He had rendered very important services upon many occasions in the last two years, and his loss is sensibly felt" (Wellington to Lord Liverpool 9 April 1811)[4] He refused his parole, and was sent to Salamanca under a guard of four gendarmes.

Two days afterwards he reached the British headquarters, "where Lord Wellington, knowing his resolute, subtle character, had caused his baggage to be brought, observing that he would not be long absent".

[6] Waters served throughout the Peninsular War, being present at Porto, Talavera, Bussaco, Ciudad Rodrigo, Badajoz, Salamanca, Vittoria, the battle of the Pyrenees (during which he was wounded while speaking to Wellington), the Nivelle and Nive, Orthes and Toulouse.