Leafhopper is a common name applied to any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs or trees. Their hind legs are modified for jumping, and are covered with hairs that facilitate the spreading of a secretion over the body that acts as a water repellent and carrier of pheromones. They undergo an incomplete metamorphosis and have various host associations varying from very generalized to very specific. Some species have a cosmopolitan distribution, or occur throughout the temperate and tropical regions. Some are pests or vectors of plant viruses and phytoplasmas. The family is distributed all over the world, and constitutes the second-largest hemipteran family with at least 20,000 described species.

They belong to a lineage traditionally treated as infraorder Cicadomorpha in the suborder Auchenorrhyncha, but as the latter taxon is probably not monophyletic, many modern authors prefer to abolish the Auchenorrhyncha and elevate the cicadomorphs to a suborder Clypeorrhyncha. The tribe Proconiini of the subfamily Cicadellinae is commonly known as sharpshooters.