Neutron powder diffraction results on the tetragonal-orthorhombic and orthorhombic-monoclinic structural phase transitions of tungsten oxide are reported. The observed first-order transition from P4/ncc to Pnma at 980 K to 1200 K hides the transition from the higher-temperature phase P4/nmm (via Cmca) to Pnma. At 623(24) K, Pnma transforms via octahedral rotations in a tricritical transition to P2₁/n. The structural characteristics and thermodynamic properties of the order parameters are described in detail. The evolution of the WO₆ octahedra and the atomic positions is documented using such parameters as the octahedral elongation, octahedral variance and the off-centre displacement vectors for the tungsten atoms. It is shown that the phase transitions can be adequately described within the framework of a decoupled mean-field Landau theory.