David "Zeb" Cook is an American game designer, best known for his work at TSR, Inc., where he was employed for over fifteen years. Cook designed several games, wrote the Expert Set for Dungeons & Dragons, worked as lead designer of the second edition of Advanced Dungeons & Dragons, and invented the Planescape setting for AD&D. He is a member of the Origins Hall of Fame.

The Expert Set is an expansion boxed set for the Dungeons & Dragons fantasy role-playing game. It was first published in 1981 as an expansion to the Basic Set.