The Geobacillus icigianus G1w1(T) strain was isolated from sludge samples of unnamed vaporing hydrothermal (97°С) outlets situated in a geyser in the Troinoy region (Valley of Geysers, Kronotsky Nature Reserve, Kamchatka, Russian Federation; 54°25'51.40″N, 160°7'41.40″E). The sequenced and annotated genome is 3,457,810 bp and encodes 3,342 genes.