壕沟（Trench）泛指一条长型的凹地，可为人工，也可为天然。

壕沟是军事防御工事中常见的一种，早期常用于断绝敌军据点的对外交通以便进行围困，而随着投射兵器的普及和精准度提高，挖掘壕沟来保护官兵免于伤害的战术也被广泛使用。近代化的壕沟工事在克里米亚战争及美国内战中开始出现，而第一次世界大战的西线战场则堪称壕沟战的代表性战事。

A trench is a type of excavation or depression in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared to its length (as opposed to a simple hole).

In geology, trenches are created as a result of erosion by rivers or by geological movement of tectonic plates. In the civil engineering field, trenches are often created to install underground infrastructure or utilities (such as gas mains, water mains or telephone lines), or later to access these installations. Trenches have also often been dug for military defensive purposes. In archaeology, the "trench method" is used for searching and excavating ancient ruins or to dig into strata of sedimented material.