Photocatalytic water splitting to form H₂ and O₂ using illuminated semiconductors under sunlight is one of the most promising options to produce fuels from renewable resources. Numerous attempts have been made to develop photocatalysts that function under visible light irradiation to efficiently utilize solar energy. Current successful photocatalytic systems for overall water splitting can be divided into two primary approaches. One approach is to split water into H₂ and O₂ using a single visible-light-responsive photocatalyst with a sufficient potential to achieve overall water splitting. The other approach is to apply a two-step excitation mechanism using two different photocatalysts and a reversible electron donor/acceptor pair, which was inspired by natural photosynthesis in green plants and is called the Z-scheme. This chapter describes the recent development of water-splitting photocatalytic materials (especially in the last five years), with a focus on metal oxide-based materials with appropriate modifications to reduce electron–hole recombination, to promote photoredox catalysis, and to utilize more visible photons.