Grasshoppers are insects of the order Orthoptera, suborder Caelifera. They are sometimes referred to as short-horned grasshoppers to distinguish them from the katydids (bush crickets). Grasshopper species which change colour and behaviour at high population densities are called locusts.

Grasshoppers are plant-eaters, sometimes becoming serious pests of cereals and other crops, especially when they swarm in their millions as locusts and destroy crops over wide areas. They protect themselves from predators by camouflage; when detected, many species attempt to startle the predator with a brilliantly-coloured wing-flash while jumping with their strong hind legs and (if adult) also flying, usually for a short distance. Other species such as the rainbow grasshopper have warning coloration which deters predators.

Grasshoppers have had a long relationship with humans, featuring as food, as pests, and in art, symbolism and literature.