A burial vault is a sturdy box designed to protect the coffin inside of it. The body is placed within the coffin, which is then placed inside the vault. Body, coffin, and vault are buried. A burial vault serves as an outer enclosure for buried remains, the coffin serves as an inner enclosure.

Vaults are made of either concrete, plastic or metal. Unlike a burial liner, which only covers the top and sides of the coffin, a vault completely encloses a coffin. Burial vaults are primarily used to keep the weight of the ground from crushing a buried coffin, and also to keep the ground above from sinking in. Manufacturers also state that their vaults can be sealed to keep water and other elements out. In many cases, cemeteries require either a vault or liner to keep the ground over grave sites from sinking in. This gives the ground a neat and even appearance, and helps reduce the chance of a person tripping on sunken ground.

Regardless of whether or not the body is embalmed, a vault will not prevent decomposition of the body.