土壤盐化（英语：soil salinization，又称土壤盐碱化）是常发生于气候炎热、干燥，实施灌溉却排水不良之沙漠及沿海地区等农牧业地区的现象。盐害会危害建筑物、公共设施以及出土遗迹。中国北方和印度的旁遮普地区也为此问题所苦。

沙漠空气中的水份少但水份蒸发量却很大，当蒸发量大于降雨量和地下水下渗量时，土壤中含盐分和碱的地下水受蒸发作用（毛细管作用）而被引到地上。然而，水中的盐份仍留在陆地表面或建筑物内结晶，最终可能使建筑物的砖头粉碎。盐分和碱含有强碱性的钠离子，对植物生长极为不利，当其上升至表土时，植物便无法生长，常造成极大的农业损失。

Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the gradual withdrawal of an ocean. It can also come about through artificial processes such as irrigation.