An infrared thermometer is a thermometer that infers temperature from being measured from a portion of thermal radiation sometimes called black body radiation emitted by an object. They are sometimes called laser thermometers because lasers are used to help aim thermometers, or non-contact thermometers or temperature guns, to describe a device's ability to measure temperature from a distance. By knowing the infrared energy emitted by an object and its emissivity, the temperature of an object can often be determined within a certain range of its actual temperature. Infrared thermometers are a subset of devices called "thermal radiation thermometers."

Some typical situations are when the object being measured is moving; the object is surrounded by an electromagnetic field, such as induction heating; the object is contained in a vacuum or other controlled atmosphere; or in applications that require fast response, an accurate surface temperature or high object temperature is required At the recommended point of use of the contact sensor, or contact with the sensor can damage the object or the sensor, or introduce significant temperature gradients across the surface of the object.