The Extreme Ultraviolet Sensor (EUVS) is one of the two primary instruments in the Extreme Ultraviolet and X-Ray Irradiance Sensors (EXIS) suite on the GOES-18 spacecraft. EUVS measures solar spectral irradiance at selected extreme ultraviolet, far ultraviolet, and middle ultraviolet wavelengths.

EUVS consists of three grating spectrographs, designated A, B, and C. EUVS-A measures solar emission in the 25-32 nm wavelength range, EUVS-B measures emission in the 115-141 nm range, and EUVS-C measures emission near 280 nm. The measurements include solar irradiances at selected emission lines and the Mg II core-to-wing ratio. The EUVS measurements are also used to reconstruct the solar extreme ultraviolet spectrum from 5 to 127 nm.

EUVS observations are used to monitor variations in solar ultraviolet irradiance that affect the Earth's ionosphere and thermosphere, including changes associated with solar flares and longer-term solar variability.