Reconnaissance Blind Chess (RBC) is a chess variant designed for new research in artificial intelligence. RBC includes imperfect information, long-term strategy, explicit observations, and almost no common knowledge. These features appear in real-world scenarios and challenge even state-of-the-art algorithms. Each RBC player controls traditional chess pieces but cannot directly see the locations of their opponent's pieces. Rather, a player learns partial information each turn by privately sensing a chosen 3×3 area of the board.