A zoological garden, or zoo for short, is a place where wild animals are cared for and exhibited to the public.

The first zoos were private menageries, usually belonging to kings. After the French Revolution, the Paris zoo was opened to the public.

Over time, the mission of zoos has shifted from simply displaying exotic animals, to scientific study (London Zoo was the world's first scientific zoo in 1828), and, latterly, to breeding them, and in particular maintaining populations of animals that are endangered or even extinct in the wild.

Most modern zoos keep animals in naturalistic enclosures. These enclosures are large enough for the animals to exercise in, and to have some privacy. Zoo visitors occasionally find this frustrating, but overall the experience is improved both for the animals and for the people who come to see them. Recent clever designs encourage the animals to prefer locations where they can be observed without being aware of it, for instance by having a darkened viewing window at the back of a shelter where the animals go to escape mid-day heat.

Many zoos now have special buildings for nocturnal animals, with dim red lighting during the day, so the animals will be active when visitors are there, and bright lights at night to ensure that they sleep.

A petting zoo features a combination of domestic animals and some wild species that are docile enough to touch and feed. Petting zoos are extremely popular with small children. In order to ensure the animals' health, the food is supplied by the zoo, either from vending machines or a kiosk nearby. In addition to independent petting zoos, also called children's farms, many general zoos contain one.

Sometimes monkeys are not separated from the public, e.g. in the Apenheul zoo in Apeldoorn. Peafowl are also frequently allowed to roam free in zoos.

Nearly all large cities of the world have zoos, though of drastically varying size and quality. Major zoos are important tourist attractions, sufficiently so that governments may underwrite or subsidize the zoo's operating expenses. Public funding of zoos is also justified by their educational value, and they are a common destination for school field trips. However, most zoo funding primarily comes from donations and entrance fees.

A person who looks after animals in a zoo is called a zookeeper.

See also: List of zoos, Wildlife park, Aquarium, Marine park