表面皿（英语：Watch glass）是实验室中使用的一种玻璃器皿。外形是一片微凹陷的圆玻璃片。用来蒸发、结晶内盛的少量物质，或者覆盖在烧杯上口，防止灰尘进入（但不造成密封）。

A watch glass is a circular concave piece of glass used in chemistry as a surface to evaporate a liquid, to hold solids while being weighed, as a cover for a beaker, and for heating a small amount of substance. The latter use is generally applied to prevent dust or other particles entering the beaker; the watch glass does not completely seal the beaker, so gas exchanges still occur.