包气带(Vadose zone)是指位于地球表面以下、潜水面以上的地质介质。有时人们也把包气带称为非饱和区（unsaturated zone），但是这两个概念的含义不完全相同。非饱和区一般不包括潜水面之上的毛细上升区（capillary fringe）和季节性饱和区域。

The vadose zone, also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure ("vadose" is from the Latin for "shallow"). Hence, the vadose zone extends from the top of the ground surface to the water table.