beta-V2O5, obtained by a high-temperature high-pressure method, exhibits a layered structure that favours the insertion of Na+ In this work, we report the electrochemical insertion of sodium in high pressure beta-V2O5 and its performance as cathode material for sodium-ion batteries. The material shows a first discharge capacity of 132 mAh g(-1) in the 3.6-2.0 V range at a C/20 current density and a maximum capacity of 147 mAh g(-1) under equilibrium conditions, corresponding to the insertion of 1 Na+ ion per formula unit. The beta-V2O5//Na cell delivers a specific energy as high as 370-410 Wh kg(-1). The amount of inserted sodium points to the reduction of 50% of the available V5+ ions. After 20 cycles, the discharge capacity retains 86% of the initial capacity. Concerning the reaction mechanism of high pressure beta-V2O5 upon sodium insertion/de-insertion, several phase transitions are inferred from the voltage-composition profile. Ex situ XRD reveals the appearance of several NaxV2O5 phases in the 0 <= x <= 1 compositional range, which are closely related with the non-sodiated high pressure beta-V2O5 structure. An irreversible structural transformation occurs during the very first inserted sodium, at the beginning of the first discharge, and the original high pressure beta-V2O5 structure is not recovered upon full Na+ extraction. Electrochemical performances are outstanding though.