应变片（英语：strain gauge, strain gage）是一种用来测量物体应变的测试工具。1938年，它先后由Edward E. Simmons和Arthur C. Ruge各自独立地发明出来。一般地，应变片由绝缘基片与金属敏感栅组成。应变片需要使用正确的粘合剂与物体相连接，比如502胶水。当被测部件受外力变形时，敏感栅也随之变形，因此敏感栅的电阻值会产生相应的变化。通过惠斯通电桥可以测量到这个微小的阻值变化量，而通过应变片生产厂商标明的应变片系数可将测量得到的电阻变化量转换成实际应变值。

A strain gauge (or strain gage) is a device used to measure strain on an object. Invented by Edward E. Simmons and Arthur C. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.