The basking shark ("Cetorhinus maximus") is the second-largest living shark, after the whale shark, and one of three plankton-eating shark species, along with the whale shark and megamouth shark.

Adults typically reach 7.9 m (26 ft) in length. They are usually greyish-brown, with mottled skin. The caudal fin (tail fin) has a strong lateral keel and a crescent shape.

The basking shark is found in all the world's temperate oceans. Its name derives from its habit of feeding at the surface, appearing to be basking in warmer water.

It has anatomical adaptations for filter-feeding such as a greatly enlarged mouth and highly developed gill rakers. The gill rakers, dark and bristle-like, are used to catch plankton as water filters through the mouth and over the gills.

The teeth are numerous and very small, and often number 100 per row. The teeth have a single conical cusp, are curved backwards, and are the same on both the upper and lower jaws. This species has the smallest weight-for-weight brain size of any shark, reflecting its relatively passive lifestyle.

Despite their large size and threatening appearance, basking sharks are not aggressive and are harmless to humans. The basking shark has long been a commercially important fish, as a source of food, shark fin, animal feed, and shark liver oil. Overexploitation has reduced its populations to the point where some have disappeared and others need protection.

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