Tributyltin oxide (TBTO) is an organotin compound chiefly used as a biocide (fungicide and molluscicide), especially a wood preservative. Its chemical formula is [(C<sub>4</sub>H<sub>9</sub>)<sub>3</sub>Sn]2O. It is a colorless viscous liquid. It is poorly soluble in water (20 ppm) but highly soluble in organic solvents. It is a potent skin irritant.
Historically, tributyltin oxide's biggest application was as a marine anti-biofouling agent. Concerns over toxicity of these compounds have led to a worldwide ban by the International Maritime Organization.[1] It is now considered a severe marine pollutant and a Substance of Very High Concern by the EU.[2] Today, it is mainly used in wood preservation.[3]