Technical Abstract: The strawberry genus, Fragaria (Rosaceae), has a basic chromosome number of x = 7. The ploidy levels of natural wild strawberry species, include diploid (2n = 2x = 14), tetraploid (2n = 4x =28), pentaploid (2n = 5x = 35), hexaploid (2n = 6x = 42), octoploid (2n = 8x = 56), and nonaploid (2n = 9x = 63) plants. Artificial triploid (2n = 3x = 21), tetraploid, pentaploid, octoploid, decaploid (2n = 10x =70), 16-ploid, and 32-ploid plants have been constructed in the laboratory and grown in cultivation. Hitherto, F. iturupensis Staudt, a species with limited distribution on Atsunupuri Volcano, Iturup Island, of the Kurile Islands, Sakhalin Territory, in the Russian Federation, has been described as octoploid. Surprisingly, our research, using chromosome analysis and flow cytometry revealed that F. iturupensis includes naturally occurring decaploid genotypes with 2n = 10x = 70 chromosomes. This is the first report of a naturally occurring decaploid strawberry species.