Macaques are a genus of Old World monkeys found ranging from Northern Africa to Japan. Old World monkeys usually have tails, although unlike New World monkeys, their tails are not prehensile. Some individual macaque species lack tails, earning them the common name of ape, although this nomenclature is technically incorrect. Macaques are the most widespread non-human primate genus, and several species, such as Rhesus Macaques and Barbary Macaques, are well known to humans.

Macaques are frequently used in animal experimentation, especially Rhesus Macaques, which are easy to keep in captivity. Numerous famous discoveries and experiments have involved Rhesus Macaques, ranging from the Rhesus factor in blood to infamous experiments on maternal deprivation carried out in the 1950s. Rhesus Macaques generally live approximately 25 years, and in nature, they prefer a wide range of environments, including grasslands, woodlands, and urban areas. Rhesus Macaques tend to be bold and intelligent.

Barbary Macaques, also called Barbary Apes because they lack tails, inhabit Morocco and Algeria. A small colony of Barbary Macaques, likely introduced, inhabits Gibraltar. Barbary Macaques are listed as under threat, due to increased logging activity and killing by farmers and villagers. A popular myth holds that as long as Barbary Macaques live on Gibraltar, the British will retain rule there.

All macaques tend to lead social lives in troops ranging from 20 to 200, with a mixture of males and females. Females tend to outnumber males, with most troops following a matriarchal leadership structure. Many are very loud, and fights between males are not infrequent, while most females work cooperatively with one another. Macaques also exhibit sexually dimorphic tendencies, with males visually distinguishable from females in most species.

Pet and captive macaques tend to carry diseases thanks to their confinement, especially a rare form of herpes that is not harmful to macaques but can be very damaging to humans if it crosses species. As a result, individuals who handle macaques should use protection, including gloves and masks, and should make sure that they are fully vaccinated. Macaques kept in captivity should also be properly cared for to minimize the risk of spreading such diseases.