The following outline is provided as an overview of and topical guide to sharks:

Sharks (superorder Selachimorpha) are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 440 million years ago, before the time of the dinosaurs.^[1]

• Ichthyology – branch of zoology devoted to fish (including sharks)
• Meristics – branch of ichthyology that relates to counting features of fish, such as the number of fins or scales

A shark, also called a "selachimorph", can be described as all of the following:

• Animal – multicellular, eukaryotic organism of the kingdom Animalia or Metazoa. An animal's body plan eventually becomes fixed as it develops, although some types of animal undergo a process of metamorphosis later on in their life. Most kinds of animal are motile, meaning they can move spontaneously and independently.
  • Chordate – Chordates (phylum Chordata) are animals which are either vertebrates or one of several closely related invertebrates.
    • Fish – gill-bearing aquatic vertebrate (or craniate) animal that lacks limbs with digits.
      • Chondrichthye (cartilaginous fish) – jawed fish with paired fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone.
        • Elasmobranch – member of the subclass Elasmobranchii, which includes sharks, rays, and skates.
• Predator – organism that attacks and feeds on prey (the organism that is attacked).^[2]
  • Apex predator – some shark species are apex predators, that is, predators with no predators of their own, residing at the top of their food chain.^[3]

List of sharks Subdivisions of the biological classification Selachimorpha include:

• Carcharhiniformes – ground sharks
• Heterodontiformes – bullhead sharks
• Hexanchiformes – the five extant species of the most primitive types of sharks
• Lamniformes – mackerel sharks
• Orectolobiformes – includes carpet sharks, including zebra sharks, nurse sharks, wobbegongs, and the whale shark
• Pristiophoriformes – includes sawsharks
• Squaliformes – includes gulper sharks, bramble sharks, lantern sharks, rough sharks, sleeper sharks and dogfish sharks
• Squatiniformes – angel sharks
• † Cladoselachiformes
• † Hybodontiformes
• † Symmoriida
• † Xenacanthida (Xenacantiformes)

• Predation
  • Apex predator
• Shark threat display – Behaviour shown by some sharks when threatened
• Spy hopping – Raising the head out of the water

• Physical characteristics of sharks – shark skeleton, respiration and skin
  • Dermal denticle – small outgrowths which cover the skin of sharks
  • Ampullae of Lorenzini – sensing organ that helps sharks and fish to sense electric fields
  • Electroreception – the biological ability to perceive electrical impulses (see also Ampullae of Lorenzini)
  • Lateral line – sense organ that detects movement and vibration in the surrounding water
  • Shark cartilage – material that a sharks' skeleton is composed of
  • Shark teeth
  • Spiracle – pumps water across gills
  • Clasper – the anatomical structure that male sharks use for mating
  • Fish anatomy – generic description of fish anatomy

• Drum lines
• Shark net – submerged net placed around beaches to reduce shark attacks on swimmers
• Shark proof cage – cage from which a SCUBA diver can examine sharks more safely
• Shark repellent – method of driving sharks from an area, object, person, or animal
  • Magnetic shark repellent – use of permanent magnets to repel sharks
  • Protective oceanic device – first successful electronic shark repellent
• Shark suit

• Drivers of the shark trade
• Land-based shark fishing – fishing for sharks from land such as a beach, shoreline, jetty, pier, or bridge
• Shark finning – the removal of shark fins for commercial purposes

• 1992 cageless shark-diving expedition – first publicized cageless dive with great white sharks which contributed to changing public opinions about the supposed "killing machine"
• Shark Alliance – coalition of nongovernmental organizations dedicated to restoring and conserving shark populations by improving European fishing policy
• Shark Conservation Act – proposed US law to protect sharks
• Shark sanctuary – Palau's first-ever attempt to prohibit taking sharks within its territorial waters
• Shark tourism – form of ecotourism showcasing sharks
• Shark Trust – A UK organisation for conservation of sharks

• Stronsay Beast – large, dead creature washed ashore on Stronsay, in the Orkney Islands, after a storm in 1808, later presumed to be a basking shark

• Peter Benchley – author of the novel Jaws, later worked for shark conservation
• Eugenie Clark – American ichthyologist researching poisonous fish and the behavior of sharks; popularly known as The Shark Lady
• Leonard Compagno – international authority on shark taxonomy, best known for 1984 catalog of shark species (FAO)
• Jacques-Yves Cousteau – French naval officer, explorer, ecologist, filmmaker, innovator, scientist, photographer, author and researcher who studied the sea and all forms of life in water including sharks
• Ben Cropp – Australian former shark hunter, who stopped in 1962 to produce some 150 wildlife documentaries
• Richard Ellis – American marine biologist, author, and illustrator.
• Rodney Fox – Australian film maker, conservationist, survivor of great white shark attack and one of the world's foremost authorities on them
• Andre Hartman – South African diving guide best known for free-diving unprotected with great white sharks
• Hans Hass – diving pioneer, known for shark documentaries
• Mike Rutzen – great white shark expert and outspoken champion of shark conservation; known for free diving unprotected with great white sharks
• Ron and Valerie Taylor – ex-spearfishing champions who switched from killing to filming underwater documentaries
• Rob Stewart (filmmaker) – Canadian photographer, filmmaker and conservationist. He was best known for making and directing the documentary film Sharkwater

• List of ichthyology terms
• List of megamouth shark specimens and sightings
• List of prehistoric cartilaginous fish genera
• List of sharks in the Red Sea