Two novel transition metal-doped tungsten bronze oxides, Pb 2.15 Li 0.85 Nb 4.85 Ti 0.15 O 15 (PLNT) and Pb 2.15 Li 0.55 Nb 4.85 W 0.15 O 15 (PLNW), are synthesized by high-temperature solid-state reactions. The Rietveld method using the high-resolution synchrotron radiation indicates that PLNT and PLNW crystallize in the orthorhombic polar noncentrosymmetric space group, Pmn2 1 (no. 31). As a class of tungsten bronze oxide, PLNT and PLNW retain a unique rigid framework composed of d 0 transition metal cation (Ti 4+ or W 6+ )-doped highly distorted NbO 6 octahedra along with the subsequently generated Pb/LiO 12 and PbO 15 polyhedra. Interestingly, the d 0 transition metal-doped tungsten bronzes, PLNT and PLNW, exhibit extremely large second-harmonic generation (SHG) responses of 56 and 67 × KH 2 PO 4 , respectively. The observed immeasurably strong SHG is mainly attributed to a net polarization originating from the alignment of highly distorted NbO 6 octahedra with doped transition metals in the frameworks. It is believed that doping transition metal cations at the B-site of the tungsten bronze structures should be an innovative strategy to develop novel high-performance nonlinear optical materials.