<p>This Special Issue of Synthesis of TiO<sub>2</sub> Nanoparticles and Their Catalytic Activity contains 10 research and review articles which present the recent advances in the synthesis and applications of TiO<sub>2</sub> nanomaterials for photocatalytic water splitting environmental remediation antibacterial and bioimplant. In this issue photocatalysts such as Ti<sub>2</sub>O<sub>3</sub> TiN g-C<sub>3</sub>N<sub>4</sub> and reduced graphene oxide could be combined with TiO<sub>2</sub> to form heterojunctions thus enhancing photocatalytic performance. Besides anatase TiO<sub>2</sub> rutile TiO<sub>2</sub> with oxygen vacancies also demonstrated marvelous photoluminescence emission properties. In addition the cutting-edge progress in black TiO<sub>2</sub> nanomaterials are summarized in this issue. The advances of TiO<sub>2</sub> catalysis and generation mechanism of reactive oxygen species w/o light irradiation were also concluded to analyze the safety and complexity of Ti-oxides in disinfection and bioimplants.</p>