Opuntia ficus-indica (prickly pear) is a species of cactus that has long been domesticated crop plant in economics in the arid and semiarid parts of the world.  Likely having originated in Mexico, O. ficus-indica is the most widespread and most commercially important cactus.  Common English names for the plant and its fruit are Indian fig opuntia, Barbary fig, cactus pear, and spineless cactus, among many.  In Mexican, the plant is called nopal, while the fruit is called tuna, names that may be used in American English as culinary terms.

Fig opuntia is grown primarily as a fruit crop, and also for the vegetable nopales and other uses. Most culinary references to the "prickly pear" are referring to this species. The name "tuna" is used for the fruit of this cactus, and for Opuntia in general; according to Alexander von Humboldt, it was a word of Taino origin taken into the Spanish language around 1500.

Cacti are good crops for dry areas because they convert water into biomass efficiently. O. ficus-indica, as the most widespread of the long-domesticated cactuses, is as economically important as maize and blue agave in Mexico. Because opuntia species hybridize easily, the wild origin of O. ficus-indica is likely to have been in Mexico two to the fact that its close relatives are found in central Mexico.