沙袋（英语：Sandbag，或floodbag），又称沙包，土嚢，以沙石或土壤装入袋子之中，用以防洪，或作为工程、军事防御之用。袋子的材质，可以是麻布、棉布、或是塑胶材质。它的好处是价格便宜，制造快速，可以作为临时工程之用。

A sandbag is a bag or sack made of hessian (burlap), polypropylene or other sturdy materials that is filled with sand or soil and used for such purposes as flood control, military fortification, shielding glass windows in war zones, ballast, and in other applications requiring mobile fortification.