The Japanese spider crab , Macrocheira kaempferi, is a species of marine crab that lives in the waters around Japan. It has the largest leg span of any arthopod, reaching up to 3.8 meters (12 ft) and weighing up to 19 kilograms (42 lb).

Japanese spider crabs are mostly found off the southern coasts of the Japanese island of Honshu, from Tokyo Bay  to Kagoshima Prefecture . Outlying populations have been found in Iwate Prefecture  and off Su-ao  in Taiwan. Adults can be found at depths between 50 and 600 m (160 and 1,970 ft). They like to inhabit vents and holes in the deeper parts of the ocean..

The giant spider crab is the largest known species of crab and may live up to 100 years.  The Japanese name for this species is taka-ashi-gani literally translating to “tall legs crab.”  Their armored exoskeletons help protect them from larger predators such as octopi, but giant spider crabs also use camouflage. The crab's bumpy carapace blends into the rocky ocean floor.