William Monteith, R.A., K.L.S., F.R.S., F.R.G.S. (22 June 1790 – 18 April 1864) was a British soldier, diplomatist and historian, associated with the East India Company.
William Monteith was born in the Abbey parish, Paisley, Renfrewshire, on 22 June 1790. On 18 March 1809 he was appointed a lieutenant in the Madras engineers, and became captain in that corps on 2 May 1817, lieutenant-colonel on 4 November 1824, colonel on 13 May 1839 (brevet on 18 June 1831).
Monteith accompanied Sir John Malcolm's embassy to Persia, and when at Tabriz, in February 1810, was sent to reconnoitre the Russian frontier-posts on the Aras, near Megeri, at the request of Abbas Mirza, the prince royal of Persia. When Malcolm's embassy quit Persia, Monteith was one of the officers left behind. During the Russo-Persian War, he went with Abbas Mirza to Erivan, and accompanied an expedition into Georgia, in which the Persians were unsuccessful. During the four succeeding campaigns against the Russians in 1810-13 Monteith was in command of a frontier force of cavalry with six guns, and of the garrison of Erivan. He was engaged in many skirmishes, and once was wounded. The war against Russia was supported by the British minister, Sir Harford Jones Brydges but Napoleon's retreat from Moscow brought about a reversal of British policy. When Henry Ellis and David Richard Morier concluded the treaty of Teheran between Great Britain and Persia, which was signed on 25 November 1814, and remained in force until the war of 1857, Monteith acted as secretary to Morier. He was still in Persia in 1819, and acted as aide-de-camp to Sir William Keir Grant, commanding the Bombay force sent against the Wahhabi pirates of the Persian Gulf, which destroyed their stronghold of Ras al-Khaimah. He was present with the Persians during the war with Turkey. He was then employed to ascertain the boundary between Persia and Turkey.