The paper presents an acousto-optic lunar infrared spectrometer (LIS) intended for mineralogical analysis and assessment of the hydration of the lunar surface regolith near the lander. Its optical layout, characteristics, results of calibrations and laboratory measurements are given. The LIS is designed to measure the spectrum of solar radiation reflected by the lunar surface; it will function as part of the load complex of the Luna-25 lander. The instrument is mounted on the manipulator of the lander in such a way that its field of view is within the field of view of the television support stereo cameras of the robotic arm working zone (TV RPM). The instrument operates in the spectral range of 1.15-3.4 mu m, including the OH/H2O absorption bands, with a spectral resolution of approximately 25 cm(-1). The principle of operation of the device is based on acousto-optic spectral filtering of optical radiation.