Yubaba's son. Although he has the appearance of a young baby, he is twice Yubaba's size. He is also very strong and can be dangerous. Yubaba goes out of her way to give him whatever he wants. When Zeniba turns Boh into a mouse, he becomes good friends with Chihiro and eventually stands up to Yubaba to protect Chihiro. Yubaba also becomes almost ashamed at the end when he turns back into his former self, since she had seen Boh as a mouse and regarded him a "dirty mouse".