Fly ash is a by-product of coal combustion that contains silica and has the potential to be utilized as a raw material for nanosilica. This study aims to synthesize nanosilica from fly ash using the hydrothermal method with variations in soaking temperatures of 70°C, 75°C, and 80°C. The synthesis process includes pretreatment with HCl and NaOH solutions, immersion in an ultrasonic cleaner, a…