We have studied the negative thermal expansion (NTE) behaviour of oxyphosphate V₂OPO₄ over a wide temperature range using X-ray and neutron diffraction, and have discovered that the NTE arises due to an electronic charge ordering transition from a larger-volume charge-ordered phase to a smaller-volume charge-disordered phase as temperature increases. The highly anisotropic thermal expansion is dominated by the difference in size of V²⁺ and V³⁺, with NTE most apparent along the directions of face-sharing octahedral chains. This material is unusual in remaining semi-conducting throughout the charge order transition, in contrast to many other electronically-driven NTE materials.