D. B. Weiss
"Lord Snow" was written by the show creators and executive producers David Benioff and D. B. Weiss, based on A Game of Thrones by George R. R. Martin, including chapters 18-22, 24 and 37. (Catelyn IV, Jon III, Eddard IV, Tyrion III, Arya II, Bran IV and Daenerys IV).