Holy Sigmar is an invocation of Sigmar, the patron god of the Empire in the Warhammer Fantasy setting, where priests, witch hunters and soldiers call on him for protection in battle. The phrase has become a recognisable piece of Warhammer speech through games, tabletop play and fan videos, where its old-fashioned, devout tone stands out against modern slang. Online it spread as a soundboard and meme reaction, especially among Warhammer players, because it instantly signals faith, doom or exaggerated heroism without needing any explanation.