AbstractA many-body large polaron, which is important for both fundamental physics and technological applications, has been predicted to occur in bismuth vanadate (BiVO₄). Herein, using a combination of high-resolution spectroscopic ellipsometry, X-ray absorption spectroscopy at the V L_3,2- and O K-edges, and high-resolution X-ray diffraction supported by theoretical calculations, we reveal a new many-body large-hole polaron in W-doped BiVO₄ films and the interplay of the large-hole polaron and indirect bandgap when determining the photocatalytic activity. With various W doping concentrations and temperatures, anomalous spectral weight transfers in the complex dielectric function are observed, revealing electronic correlations, particularly the on-site Coulomb interactions of O p (U_pp) and V d (U_dd), and screening in BiVO₄. Due to the distortion of BiO₈ dodecahedra and U_dd, Bi 6 s is lifted to the top of the valance band, which results in the formation of an indirect bandgap and a large-hole polaron. The large-hole polaron is found to form as a localized midgap state, consisting of O p hybridized with the V d and Bi sp orbitals, and this is important when determining the high photocatalytic activity of BiVO_4. Our results show the importance of the interplay among the charge, orbital, and lattice degrees of freedom in forming the many-body large-hole polaron, which improves the conductivity and results in a transition metal oxide with high photocatalytic activity.