Strontium titanate is a wide-band-gap perovskite semiconductor with high chemical stability and excellent electron mobility, which can be further enhanced by defect engineering or doping at the nanoscale. SrTiO₃ nanoparticles show strong photocatalytic activity under UV illumination and improved charge separation when combined with heterostructures or cocatalysts. They are therefore extensively investigated for photocatalytic hydrogen generation, CO₂ reduction, photocatalytic fuel cells, and as functional components in solid oxide fuel cells and electronic oxide heterostructures.