An experimental simulation of underground coal gasification (UCG) using large bulk samples of ortho-lignite was conducted in an ex-situ laboratory installation. The main goal of the experiment was to evaluate the suitability of the high-moisture lignite for UCG. The average moisture content of the coal feed was 46.5wt%, and its calorific value was 12.6MJ/kg. Changes in the gas composition, the gas production rates, and the distribution of temperatures in the artificial coal seam were measured over the course of the experiment. During the 120h UCG trial, gas with an average calorific value of approximately 7.2MJ/Nm3 was produced. The overall energy efficiency of the process was estimated at 59%. The study results demonstrated that exploitation of the high-moisture lignite deposits using oxygen-blown UCG may be a feasible option. Therefore, this technique may be considered as an attractive option for the extraction of low-rank Miocene ortho-lignites, large deposits of which are located in Poland and in many other countries around the world.