Stop the Express (also known as Bousou Tokkyuu SOS (暴走特急SOS, "Runaway Express SOS," in Japan) is a video game developed by Hudson Soft and published in 1983. It was written for the Sharp X1 and later ported to the ZX Spectrum, Commodore 64, and MSX. It was remade for Nintendo Family Computer as Challenger (チャレンジャー) in 1985.