Geralt of Rivia (Polish: Geralt z Rivii) is a fictional character and protagonist of The Witcher series by Polish writer Andrzej Sapkowski, as well as its adaptations.
In the stories, Geralt, the central character, is said to be one of the world's best witchers. He is said to have resisted the "changes" during his childhood better than most, which encouraged his makers to perform even more dangerous experimental procedures on him. Because of these additional procedures, Geralt lost all body pigmentation. Because of his pale skin and white hair, he is also known in Starsza Mowa (Older Speech) as "Gwynbleidd", the White Wolf.
Source: Wikipedia, "Geralt of Rivia", available under the CC-BY-SA License.