Wood preservation refers to the process of treating wood with chemicals or other biochemical substances to prevent or slow down wood degradation problems due to fungal rot or decay, sapstain, molds, or wood-destroying insects. Wood easily degrades without sufficient preservation, and there are a number of different chemical preservatives and processes that can extend the life of wood, timber, and their associated products. The goal of modern-day wood preservation is to ensure a deep, uniform penetration with reasonable cost, without endangering the environment.

Wood preservation methods include pressure treatment, thermal impregnation, and the use of preservative oils and water-soluble salts. The degree of protection achieved depends on the type of preservative used, the penetration of the preservative into the wood, and the retention of the preservative in the wood.

Wood preservatives are commonly used for outdoor applications such as seasoned building materials, utility poles, fence posts and rails, structural members, structures and dwellings, transportation vehicles, crop containers, lawn furniture and decks, playground equipment, garden/landscape timbers, and log homes. However, the treatment process and the use of treated products can result in risks to human health and the environment.

Proper application of preservatives can prolong the service life of wood for many years, reduce wood losses, and help to conserve timber resources. An estimated 10% of the timber cut each year in the United States is used to replace wood that has failed, often due to attack by fungi, bacteria, insects, or marine borers.