Valentine Wiggin is a fictional character in Orson Scott Card's Ender's Game series of novels. She is the older sister of Ender Wiggin.

Valentine was born because the International Fleet decided that the eldest child, Peter, was too brutal for the possiblity of Battle School. The International Fleet then decided to let the Wiggin family bear a girl with the same brilliance as Peter, only milder. However, the girl became too mild and lacked the ability of violence altogether. It was then that they requisitioned Ender.

While Ender was away in Battle School, Valentine was forced to work with Peter to gain influence on the nets. Valentine's pseudonym was Demosthenes, while Peter's was Locke. Demosthenes became a paranoid writer about Russian expansion. Through great pathos and demagoguery, Valentine was able to acquire a vast popularity.

After Ender's victory over the Buggers, Valentine forced Peter to let her go off to space because Peter prevented Ender from coming back to Earth so Ender could be safe. Valentine still wrote with her Demosthenes identity, but instead of being paranoid, she wrote about histories of different cultures on different planets, and in addition, she also applied some concepts to all humankind.

Under the Demosthenes pseudonym, Valentine developed a 4-tiered Hierarchy of Alienness: utlannings - strangers from one's own world; framlings - strangers of one's own species but from a different world; ramen - strangers of another species but capable of communication and peaceful coexistence (such as the Pequeninos); and varelse, an alien species incapable of peaceful coexistence (the Formics, disparagingly known as buggers, were originally thought to be varelse).

Valentine Wiggin married Jakt on the planet Trondheim, and 22 years later, she went to Lusitania to help her brother help the Pequeninos.

Physically, Valentine has been described as having blonde hair. She is two years younger than Peter and three years older than Ender.