Lieutenant-Colonel Sir William Frederick Travers O'Connor (30 July 1870 – 14 December 1943) was an Irish diplomat and officer in the British and British Indian armies. He is remembered for his travels in Asia, cartography, study and publication of local cultures and language, his actions on the Younghusband expedition to Tibet, Royal Geographic Society council member, member of the Royal Automobile Club and for his work negotiating and signing the Nepal–Britain Treaty of 1923.