Three-dimensional (3D) GeO2 nanowire networks were fabricated by using germanium as both a source material and catalyst in an oxygen-rich growth environment. The branches within one network show very regular orientation relationships: either perpendicular or parallel to each other. The nanowires follow a base-growth model and the growth direction is along <110>. The GeO2 nanowire networks exhibit strong violet emission peaked at 404 nm under a 265 nm UV light excitation.