Abstract <p>The possibility of using a laser gyroscope with circular polarization of waves and a Zeeman frequency biasing for conducting various types of geophysical measurements is investigated. The first results of measuring the Earth’s rotation rate by a Zeeman laser gyroscope with a perimeter of 20 cm in the underground laboratory of the Baksan Neutrino Observatory, Institute for Nuclear Research of the Russian Academy of Sciences (BNO INR RAS), are presented under conditions of maximum exclusion of external influencing factors—with thermal stabilization, shielding of electromagnetic fields, and minimization of seismic noise. An increase in the registration sensitivity by an order of magnitude (up to 10^–3 deg/h) is noted compared to previously experiments in the urban ground-based laboratory. The possibility of continuous operation of the installation in a remote mode for more than 6 months is shown.</p>