Niobium pentaiodide is the inorganic compound with the formula Nb2I10. It is a yellow, moisture-sensitive, diamagnetic solid. It forms upon heating metallic niobium with iodine. Its structure has been verified by single crystal X-ray diffraction, which reveals an edge-shared bioctahedral structure, as observed for many pentahalides of Nb and Ta. The bonds to the bridging iodides are 0.3 Å longer than the terminal Nb-I bonds.