A fishhook is a curved piece of metal with a sharp point at one end, designed to catch fish. The hook works because once a fish bites the bait attached to it, the curved shape and sharp barb make it very difficult for the fish to escape. Fishhooks come in many sizes: tiny ones for catching minnows and huge ones for catching marlin or tuna.

The basic design of the fishhook is ancient and remarkably clever. When a fish swallows the baited hook and tries to swim away, the point digs in deeper. Most fishhooks have a small barb near the point that angles backward, preventing the hook from sliding back out. Anglers attach fishhooks to fishing line, often adding weights called sinkers and floating markers called bobbers.

People have been using fishhooks for at least 23,000 years, making them one of humanity's oldest tools. The earliest fishhooks were carved from bone, shell, or wood. Today's metal fishhooks are stronger and sharper, but the principle remains the same.

The term also describes anything shaped like a fishhook's distinctive curve, such as a fishhook turn on a mountain road that bends sharply back on itself.