A mattress is a mat or pad, usually placed a top a bed upon which one can sleep or lie. The word mattress is derived from the arabic word "to throw". Though a mattress can be placed directly on the floor, it is usually placed atop a platform such as a bed or a metal spring foundation. Traditionally mattresses have been filled with a variety of natural materials like straw or feathers but these days some innovative companies have designed mattresses that can be filled with air or water.

Modern mattresses usually contain an innerspring core or materials such as latex, viscoelastic or other polyurethane type foams. Modern spring mattress cores, often called "innersprings" are made up of steel coil springs or "coils". A common innerspring mattress consists of three components: the spring core, the foundation and the upholstery layers.

Mattresses should be rotated approximately once every three months to ensure even wear and tear. Two sided mattresses should be flipped twice per year. Folding and bending of mattresses should be avoided as far as possible. They should never be soaked or else mildew may develop inside the upholstery. Mattress protectors should be used as they help prevent staining and soiling. Mattresses have a life of eight to ten years depending upon the wear and tear they undergo. Once a mattress starts sagging or has springs protruding through the upholstery layer it is time to change it. Mattresses should also be changed when lumpiness or squeaking begins.

Mattresses come in three varieties: soft mattresses, medium mattresses and firm mattresses. Quality of mattress is determined by various parameters like pressure distribution, edge support, skin microclimate, hygiene and long-term stability. Other factors such as firmness are more specific to the sleeper. Some leading brands offer mattresses with one softer side and one firmer side, or with adjustable firmness levels, to accommodate sleepers who share a bed.