The crystal of the title compound, C₉H₁₃N₅O₄, belongs to space group P2₁ with cell dimensions a = 4.380(2), b = 10.909(4), c = 11.601(4)Å, and β = 99.11(3)°. The final R value is 0.0583. The chain moiety corresponding to the ribose ring in guanosine does not adopt a fully extended conformation. The relative orientation of the purine ring and the ether oxygen atom is similar to that observed in one of the crystallographically independent guanosine molecules in the crystal structure of guanosine dehydrate.