On a sailboat, a forestay is a piece of standing rigging which keeps a mast from falling backwards. It is attached either at the very top of the mast, or on a bendy mast between 1/6 and 1/4 from the top of the mast. The other end of the forestay is attached at the bow of the vessel. Often a sail is attached to the forestay. One such sail is a jib or a genoa. A forestay might be made from stainless steel wire on a modern yacht, or natural fibers on an older square-rigged ship.

Contrast with backstay and shrouds.