Gabion (from Italian gabbione meaning "big cage"; from Italian gabbia and Latin cavea meaning "cage") are cages, cylinders, or boxes filled with soil or sand that are used in civil engineering, road-building, and military application. For erosion control caged riprap are used. For dams or foundation construction, cylindrical metal structures are used. In a military context, earth or sand-filled gabions are used to protect artillery crews.

The most common civil engineering use is to stabilize shore against erosion. Other uses include retaining walls, temporary floodwalls, to filter silt from runoff, and for small or temporary dams. They may be used to direct the force of a flow of flood water around a vulnerable structure. Gabions are also used as fish barriers on small streams.