African green monkeys (Chlorocebus spp.) are a genus of Old World monkeys native to the forests and savannahs of sub-Saharan Africa. They are also known as vervet monkeys, particularly in the context of the Chlorocebus pygerythrus species. These monkeys are small to medium-sized primates, with a typical body length of 40-60 cm (16-24 inches) and a tail length of about the same. They display sexual dimorphism, with males being larger than females.

African green monkeys are known for their greenish-tinged fur and distinct black face with a white fringe of hair. They are social animals, living in groups called troops, which can range from a few individuals to more than 50. Troops are led by a dominant male and consist of multiple adult females and their offspring. These monkeys are diurnal and spend most of their time foraging for food in trees or on the ground. Their diet is omnivorous, consisting of fruits, seeds, leaves, insects, and small vertebrates.

In scientific research, African green monkeys have played a significant role, particularly in the development of vaccines and the study of infectious diseases. The African green monkey kidney cell line (Vero cells) is widely used for the production of viral vaccines and for research on virus-host interactions. These monkeys have also been used as a model organism to study the biology and behavior of primates, as well as the evolution of human ancestors. However, the use of non-human primates in research is a subject of ethical debate, and efforts are being made to reduce or replace their use with alternative methods.