The Dong Feng 31 (; NATO reporting name CSS-9) is a long-range, road-mobile, three stage, Solid-fuel rocket intercontinental ballistic missile (ICBM) in the Dongfeng missile series developed by the People's Republic of China. It is designed to carry a single 1-megaton thermonuclear weapon. It is a land-based variant of the submarine-launched JL-2. It is operated by the Second Artillery Corps (SAC) which, in 2009, was estimated to have under 15 DF-31 missiles and under 15 DF-31A missiles in inventory. It is not known how many missiles of this type the SAC currently has.