风口（英语：Wind Gap），亦称风隙，是描述地形的一种地理学名词。

风口意指有二：

由于风口是交通唯一的进出口，因此在中国大陆可见有古代遗留下的城墙是位于风口地形，这城墙是做为御敌、检查之用的一道关卡，形成军事镇守要地的咽喉点。

A wind gap is a valley through which a waterway once flowed but is now dry as a result of stream capture. A water gap is a similar feature, but one in which a waterway still flows. Water gaps and wind gaps often provide practical routes for trails, roads, and railroads through mountainous terrain.