灌溉就是人为方式使用天然降水(雨水)以外的其他水源供给土地或土壤水份，多半是用来种植农作物或其他植物，也可以用来维持地貌景观，或在干燥地带或是在过度降雨后的地区进行植被重建，灌溉对农作物也有其他的好处，包括保护植物免于霜害、在粮食区抑制杂草成长，并且抑制土壤固结。不用灌溉而以雨水为唯一水源的农业称为旱田。

灌溉系统也会用来抑制灰尘、排放污水以及矿物的堆摊浸滤。灌溉系统常会和排水系统一起研究，后者是用天然或人工的方式除去某一区域地表或是地表以下的水份。

灌溉是五千多年来农业的中心特征，也是许多文化的成果，是许多国家经济及社会的基础。

Irrigation is the method in which water is supplied to plants at regular intervals for agriculture . It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growth in grain fields and preventing soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dryland farming.