A fish trap is a trap used for fishing. Fish traps may have the form of a fishing weir or a lobster trap. A typical trap might consist of a frame of thick steel wire in the shape of a heart, with chicken wire stretched around it. The mesh wraps around the frame and then tapers into the inside of the trap. When a fish swims inside through this opening, it cannot get out, as the chicken wire opening bends back into its original narrowness. In earlier times, traps were constructed of wood and fibre.

Traps are culturally almost universal and seem to have been independently invented many times. There are essentially two types of trap, a permanent or semi-permanent structure placed in a river or tidal area and bottle or pot traps that are usually, but not always baited to attract prey, and are periodically lifted out of the water.

The Mediterranean Sea, with an area of about of 2.5 million sq km (970,000 sq mi), is shaped according to the principle of a bottle trap. It is easy for fish from the Atlantic ocean to swim into the Mediterranean through the narrow neck at Gibraltar, and difficult for them to find their way out. It has been described as "the largest fish trap in the world".

A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish). At 32,000 species, fish exhibit greater species diversity than any other group of vertebrates.

Fish are an important resource worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries (see fishing) or farm them in ponds or in cages in the ocean (see aquaculture). They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.

A trap is a device or tactic intended to catch an intruder, enemy, error, or substance.

Trap may also refer to: