Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.

Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers. Commercial solutions of formaldehyde in water, commonly called formalin, were formerly used as disinfectants and for preservation of biological specimens.

For industrial applications uses, Formaldehyde is a common building block for the synthesis of more complex compounds and materials.

The textile industry uses Formaldehyde-based resins as finishers to make fabrics crease-resistant. Formaldehyde-based materials are key to the manufacture of automobiles, and used to make components for the transmission, electrical system, engine block, door panels, axles and brake shoes.

Formaldehyde is also a precursor to polyfunctional alcohols such as pentaerythritol, which is used to make paints and explosives.

For disinfectant and biocide uses, An aqueous solution of formaldehyde can be useful as a disinfectant as it kills most bacteria and fungi (including their spores). Formaldehyde solutions are applied topically in medicine to dry the skin, such as in the treatment of warts. Many aquarists use formaldehyde as a treatment for the parasites Ichthyophthirius multifiliis and Cryptocaryon irritans.

Formaldehyde is used to inactivate bacterial products for toxoid vaccines (vaccines that use an inactive bacterial toxin to produce immunity). It is also used to kill unwanted viruses and bacteria that might contaminate the vaccine during production.

Some topical creams, cosmetics and personal hygiene products also contain derivatives of formaldehyde as the active ingredients that prevent the growth of potentially harmful bacteria.

Formaldehyde is used extensively in the woodworking and cabinet-making industries. It is used in the glues that bond particle-board together. The particle board is used underneath wood veneer and plastic laminate. Cabinets, bank counters, and veneered and laminated woodwork all use particle board containing Formaldehyde under the plastic laminate and wood veneer.