Colonel Sir William Owen Lanyon KCMG CB (21 July 1842 – 6 April 1887) was an Irish colonial administrator and British Army officer.
He became private secretary to Sir John Peter Grant, Governor of Jamaica from 1868 to 1873, and was invalided in the Ashanti campaign in West Africa.
The neighbouring Cape Colony, semi-independent and the largest state in the region, was considered the only local entity with the resources to govern Griqualand West.
The Cape Prime Minister John Molteno, after repeatedly refusing to annex the costly and unstable territory, eventually consented to incorporate it.
He then took over administration of Transvaal from Sir Theophilus Shepstone on 4 March 1879, and assisted the Governor Henry Bartle Frere in dealing with the restive Boer population.