We report here the Raman spectrum and lattice dynamics study of a well-crystallized β-V ₂O ₅ material prepared via a high-temperature/high-pressure (HT/HP) route, using α-V ₂O ₅ as the precursor. Periodic quantum-chemical density functional theory calculations show good agreement with the experimental results and allow one to assign the observed spectral features to specific vibrational modes in the β-V ₂O ₅ polymorph. Key structure-spectrum relationships are extracted from comparative analysis of the vibrational states of the β-V ₂O ₅ and α-V ₂O ₅ structures, and spectral patterns specific to the basic units of the two V ₂O ₅ phases are proposed for the first time. Such results open the way for the use of Raman spectroscopy for the structural characterization of vanadium oxide-based host lattices of interest in the field of lithium batteries and help us to greatly understand the atomistic mechanism involved in the α-to-β phase transition of vanadium pentoxide.