Motivated by fundamental interests and practical applications, three-dimensional (3D) photocatalysts are a fascinating area of research in clean energy. Based on first-principles calculations, we predicted three new 3D polymorphs of TiO2: δ-, ε-, and ζ-TiO2. Our results indicate that the band gaps of TiO2 decrease almost linearly with an increase in the coordination number of Ti. Moreover, δ-TiO2 and ζ-TiO2 are semiconductors, whereas ε-TiO2 is a metal, and the lowest energy of ζ-TiO2 is a quasi-direct band gap semiconductor with a distinctive band gap of 2.69 eV, calculated by the HSE06 level. In addition, the calculated imaginary part of the dielectric function indicates that the optical absorption edge is located in the visible light region, suggesting that the proposed ζ-TiO2 may be a good photocatalyst candidate. Importantly, ζ-TiO2 with the lowest energy is dynamically stable, and phase diagrams based on total energies at a specific pressure indicate that ζ-TiO2 can be synthesized from rutile TiO2 at high-pressure conditions.