水火箭是一种以水的压力推进的模型火箭。

水火箭运行原理与火箭大致相同。发射水火箭前需要先用泵令其内部充满水，水火箭内的压力太大时水会向外喷射。根据牛顿运动第三定律，当水火箭喷出水时，会产生同等大小，方向相反的反作用力，这力会推动水火箭向上运动。

A water rocket is a type of model rocket using water as its reaction mass. Such a rocket is typically made from a used plastic soft drink bottle. The water is forced out by a pressurized gas, typically compressed air. Like all rocket engines, it operates on the principle of Newton's third law of motion.