Global water scarcity and pollution present critical challenges for human society. Solar-driven wastewater treatments, such as photocatalytic degradation of organic pollutants and photothermal conversion water evaporation, offer promising solutions. TiO₂ has garnered extensive attention in these fields, but its large bandgap limits light absorption, affecting its performance and broader applications in energy and environmental fields. Consequently, modifying TiO₂ to improve its photocatalytic and photothermal conversion performance has become a research hotspot. Among various modification strategies, self-doping with Ti³⁺ and oxygen vacancies can reduce the bandgap of TiO₂, improve sunlight utilization, and increase the separation efficiency of photogenerated electron–hole pairs, thereby significantly enhancing the photocatalytic and photothermal conversion performance. This review focuses on the inorganic chemical reduction methods for preparing Ti³⁺/oxygen vacancies self-doped TiO₂ and their current applications in solar-driven photothermal conversion water evaporation. It highlights the challenges faced during synthesis and application while offering insights into future development prospects. This review is expected to provide a valuable reference for further research on the preparation and application of Ti³⁺/oxygen vacancies self-doped TiO₂.