**Abstract**

Natural titanium dioxide (TiO2) occurs in three distinct polymorphs (rutile, anatase, and brookite). Currently, TiO2 gained the attention of several researchers around the world. TiO2 is used in several applications because of its excellent properties (structural, optical, electrical, chemical, non toxic, etc.). Thus, the applications are influenced by its surface, size, morphology, and crystal phase. TiO2 as photocatalyst is widely used in energy and eco-friendly applications involving water purification, hydrogen production, phenol degradation, etc. The novelty of the present chapter lies in explaining the recently reported methods that are used to synthesize TiO2 nanoparticles, such as sol-gel, hydrothermal, precipitation, etc. The different properties of TiO2 are also provided in this chapter.

**Keywords:** titanium dioxide nanoparticles, properties, synthesis, structure, natural titanium dioxide (TiO2)
