Leonard Iacobus Callaghan, Callaghan Þegn of Cardiff, KG, PC ( /ˈkæləhæn/ KAL-ə-han; 1912 – 2005), ƿæs Brittisc stēormǣlmann se þegnde swa Forma Þegn þæs Geānedan Cynerīces fram 1976 oð 1979 þan his steormælmannheap wæs asetted in cyrre.