Foamboard is a composite made by layering styrofoam between paper or plastic to create a lightweight, sturdy material which can be used for a variety of things. It is also sometimes seen marketed as foamcore, and comes in a variety of colors, thicknesses, and strengths. Most art supply stores carry foamboard, as do some home and office supply companies. As a general rule, foamboard comes in standardized sizes which the end user must cut down to fit.

The styrofoam core of foamboard can be made in varying degrees of density. More dense styrofoam will hold up longer, but will make the foamboard much heavier. Lighter styrofoam is favored for most projects. The outer layers of foamcore are usually made with a heavyweight paper, although lightweight cardboard may sometimes be used. Both matte and glossy variations are available, and white and black are the two most common colors.

A sheet of foamboard is much sturdier than a comparable sheet of paper or cardboard. However, foamboard can still bend or warp. For this reason, a supportive backing is needed for extremely large pieces of foamboard. Foamboard is also not considered to be archival, since the papers used may be acidic, so it should not be used as a backing for valued artwork.

There are a number of potential applications for foamboard. It is ideally suited to signs and displays, since it comes in large sheets and it can be painted or decorated. Crafters can also glue things to foamboard. In sign format, foamcore can be mounted on a stick for carrying, hung in a window, or attached to a wall. It is often used for displays in classrooms and informational fairs.

Although crafters and teachers use a great deal of foamboard, other professionals find it useful as well. Architectural models are sometimes built using foamboard, and artists may use it to mount secondary prints or other less valuable projects. Foamboard can also be used as a base layer for sculpture projects.

Working with foamboard does require some skill. An extremely sharp knife should be used against a hard surface to ensure clean, even cuts. Dull knives tend to make ragged cuts, tearing the paper covering rather than slicing through it. In addition to looking unsightly, these cuts can catch on things and tear, pulling part of the facing of the foamboard off. A sharp razor and a metal ruler to use as a cutting guide are highly useful tools for foamboard projects.