Provided are a temperature sensor, an array substrate, and a display device. In the temperature sensor, a low-pass filter is disposed between a ring oscillator and a comparator, so that a square-wave signal output from the ring oscillator passes through the low-pass filter and a high-frequency component in the square-wave signal output from the ring oscillator is directly filtered out by the low-pass filter, thereby improving a signal-to-noise ratio of the ring oscillator and a test accuracy of the temperature sensor.