Cadia is a planet based in the Warhammer 40,000 tabletop strategy game.

Cadia is a fortress world, on the very edge of the Eye of Terror . It has borne the brunt of many battles, and has defended the Imperium of Man against the ravening hordes of Chaos. It is here that, during the Thirteenth Black Crusade, Abaddon the Despoiler, Warmaster of the Chaos Legions, brought down his armies in an orgy of fire and destruction.

Cadia is the home of the Imperial Guard Cadian Shock Troop regiments, widely regarded as the best soldiers in the Imperium short of the superhuman Space Marines . Their leader is the indomitable Ursarkar E. Creed, the saviour of Cadia and hero of the Battle for Cadia.