层云(Stratus，简称St)是云的一种，形状为层状，分部较大，属低云族，一般高度低于2000公尺。如身处于层云中，感觉即类似于雾，因此层云也被称为“高雾”。

在一定条件下层云几乎能够达到地面。层云完全没有结构，它由细小的水珠组成。层云中往往会落下细雨或者细雪，但是不会下大雨。一般在风比较静的气象条件下会形成层云。在气温非常低的状况下甚至可能出现光晕。

层云可以分薄幕状云和碎云，此下还可以分蔽光云、透光云和波状云。

层云

被照射的层云（碎云）

苏黎世湖上的层云

罗纳河谷上的层云，云层位于800至1600米之间

Stratus clouds are low-level cloud characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds that are formed by rising thermals. More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color from dark gray to nearly white. The word "stratus" comes from the Latin prefix "strato-", meaning "layer". Stratus clouds may produce a light drizzle or a small amount of snow. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes over a region. Some call these clouds "high fog" for the fog-like cloud. While light rain may fall, this cloud does not indicate much meteorological activity.