Data on oxygen‐isotope composition of ice, together with the results of structural and textural analyses allow one to identify the genesis of ice bodies. Of all the types of underground ice in a particular region, ice of glacier origin has the lightest isotope composition. The paper presents the results of oxygen isotope analysis of samples taken from two cores extracted from different parts of a massive ground ice body, Ledyanaya Gora, located on the banks of the Yenisey River near the Arctic Circle. Comparison of these data with δ δ18values from surface waters and ground ice in the Yenisey North and from present‐day glaciers on Severnaya Zemlya, indicates that the isotope composition of the ice of the Ledyanaya Gora differs from all these other types of H2O from the area, with the greatest negative values; it is comparable only to the isotope composition of present winter precipitation on Severnaya Zemlya. It is concluded that the oxygen isotope method is very promising in terms of investigating ground ice bodies.