Valentine Wiggin aka Demosthenes was a recurring character in Orson Scott Card's four-part Ender's Game series.

Valentine was the elder sister of the protagonist, Andrew 'Ender' Wiggin, and younger sister of Peter Wiggin aka Locke aka the Hegemon of Earth.

Within the context of the novels, Valentine was rejected for Battle School because she was too mild, whereas Peter was too violent. Her mildness was the reason Ender was born, in a time when a third child was both excessive and illegal without State sanction.

From her teen years Valentine wielded a great deal of influence as the mysterious popular writer Demosthenes, in league with and under the dominance of Peter, who wrote as the highbrow writer Locke.