Medium-density fiberboard (MDF) is an engineered wood panel made by breaking down hardwood or softwood residuals into wood fibers, MDF is generally denser than plywood. It is made up of separated fibers, but can be used as a building material similar in application to plywood. It is stronger, and denser, than particle board. The name derives from the distinction in densities of fiberboard. Large-scale production of MDF began in the 1980s, in both North America and Europe.

MDF does not contain knots or rings, making it more uniform than natural woods during cutting and in service. However, MDF is not entirely isotropic, since the fibers are pressed tightly together through the sheet. Typical MDF has a hard, flat, smooth surface that makes it ideal for veneering, as no underlying grain is available to telegraph through the thin veneer as with plywood. A so-called "premium" MDF is available that features more uniform density throughout the thickness of the panel. 

MDF may be glued, doweled, or laminated. Typical fasteners are T-nuts and pan-head machine screws. Smooth-shank nails do not hold well, and neither do fine-pitch screws, especially in the edge. Special screws are available with a coarse thread pitch, but sheet-metal screws also work well. MDF is not susceptible to splitting when screws are installed in the face of the material, but due to the alignment of the wood fibers, may split when screws are installed in the edge of the board without pilot holes.