Drosophila (/drəˈsɒfɪlə, drɒ-, droʊ-/), from Ancient Greek δρόσος (drósos), meaning "dew", and φίλος (phílos), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit. They should not be confused with the Tephritidae, a related family, which are also called fruit flies (sometimes referred to as "true fruit flies"); tephritids feed primarily on unripe or ripe fruit, with many species being regarded as destructive agricultural pests, especially the Mediterranean fruit fly.

One species of Drosophila in particular, Drosophila melanogaster, has been heavily used in research in genetics and is a common model organism in developmental biology. The terms "fruit fly" and "Drosophila" are often used synonymously with D. melanogaster in modern biological literature. The entire genus, however, contains more than 1,500 species and is very diverse in appearance, behavior, and breeding habitat.

The term "Drosophila", meaning "dew-loving", is a modern scientific Latin adaptation from Greek words δρόσος, drósos, "dew", and φίλος, phílos, "loving".

Drosophila species are small flies, typically pale yellow to reddish brown to black, with red eyes. When the eyes (essentially a film of lenses) are removed, the brain is revealed. Drosophila brain structure and function develop and age significantly from larval to adult stage. Developing brain structures make these flies a prime candidate for neuro-genetic research. According to a study published in Nature in October 2024, by the scientists examining the brain of an adult female Drosophila, the shape and location of each of its 130,000 neurons and 50 million synapses were identified. In this study, the most detailed analysis ever conducted on the brain of an adult animal is represented. Many species, including the noted Hawaiian picture-wings, have distinct black patterns on the wings. The plumose (feathery) arista, bristling of the head and thorax, and wing venation are characters used to diagnose the family. Most are small, about 2–4 millimetres (0.079–0.157 in) long, but some, especially many of the Hawaiian species, are larger than a house fly.

Environmental challenge by natural toxins helped to prepare Drosophilae to detox DDT, by shaping the glutathione S-transferase mechanism that metabolizes both.

The Drosophila genome is subject to a high degree of selection, especially unusually widespread negative selection compared to other taxa. A majority of the genome is under selection of some sort, and a supermajority of this is occurring in non-coding DNA.

Effective population size has been credibly suggested to positively correlate with the effect size of both negative and positive selection. Recombination is likely to be a significant source of diversity. There is evidence that crossover is positively correlated with polymorphism in Drosophila populations.

Drosophila species are found all around the world, with more species in the tropical regions. Drosophila made their way to the Hawaiian Islands and radiated into over 800 species. They can be found in deserts, tropical rainforest, cities, swamps, and alpine zones. Some northern species hibernate. The northern species D. montana is the best cold-adapted, and is primarily found at high latitudes or high altitudes. Most species breed in various kinds of decaying plant and fungal material, including fruit, bark, slime fluxes, flowers, and mushrooms. Drosophila species that are fruit-breeding are attracted to various products of fermentation, especially ethanol and methanol. Fruits exploited by Drosophila species include those with a high pectin concentration, which is an indicator of how much alcohol will be produced during fermentation. Citrus, morinda, apples, pears, plums, and apricots belong into this category.