Thin films of LiyV2O5 (0<y<1) were made by reactive dc magnetron sputtering of V followed by electrochemical treatment in LiClO4. X-ray diffractometry showed an orthorhombic structure that varied from nanocrystalline (n-X) for unheated substrates to polycrystalline (p-X) for substrates at 180°C. Optical absorption was measured at 0.3<λ<2.5 μm. The semiconductor bandgap lay fixed at ∼0.5 μm for p-X LiyV2O5 and appeared blue-shifted in proportion with y for n-X Liy V2O 5. At λ>0.5 μm there are absorption peaks associated with V4+ ions both for p-X and n-X materials, and a broad absorption feature for p-X Liy V2O5 that is tentatively ascribed to electron hopping in the crystallographic b direction. The absorption goes up for increased y, as expected from the higher V4+ density.