Colonel Sir William Fitzwilliam Lenox-Conyngham, KCB DL JP (25 April 1824 – 4 December 1906) was an Irish militia officer.

The eldest son of William Lenox-Conyngham and Charlotte Melosina Staples, third daughter of the Rt Hon.

[1][2][3][4] He served as a Lieutenant in the 88th Regiment of Foot (Connaught Rangers), and after retiring from the Regular Army he was commissioned as a Major in the disembodied Londonderry Militia in 1848 and promoted to Lieutenant-Colonel in 1850.

[5][6] The regiment was reformed as the Londonderry Light Infantry and embodied for home defence during the Crimean War under Lenox-Conyngham as Lieutenant-Colonel Commandant, later with the honorary rank of Colonel.

[7][9] He also, after 1882, accepted the Agency of the Drapers' Company in Londonderry and in this capacity lived in the Manor House, Moneymore.