Animal shelters or what used to be known as(dog) pounds are either governmental or private organizations that provide temporary homes for stray or surrendered pet animals, most often dogs and cats, until the animal is reclaimed by the owner, adopted to a new owner, placed with another organization, or euthanized.

Unfortunately, resources are seldom adequate to support a large number of animals taken in by these organizations, so animals that are not claimed by their owners or that have temperament or health issues that cannot be corrected or treated within the resources of the organization are often euthanized. Shelters that receive a disproportionate number of animals compared to available adopters may also euthanize an animal because of space concerns.

A small number of shelters have chosen to be "no-kill" shelters, which support healthy and adoptable pets for the remainder of their lives. However, as funding is limited, the number of animals that can be accepted by the organization can be low, and some animals may not be accepted because of behavior or health concerns. No Kill shelters often do euthanize in the case of a sick animal or if there are behavioral issues. There are no clear standards for assessing these issues, and so statistics cited about how many "adoptable" animals are euthanized or adopted can be meaningless.

Some people obtain their pets from pet stores and millions of pets are taken to shelters when they get sick or are no longer wanted. Animal Welfare groups and volunteers are attempting to change that point of view by educating owners and potential owners about the lifelong commitment involved in adopting an animal, how to be a responsible pet owner, about the large number of adoptable animals available at shelters, and about the often poor condition of pet shop pets.

Animal control agencies, or nonprofit organizations contracting for animal control duties, also enforce animal-related ordinances. Some animal shelters also provide low-cost spay/neuter surgeries or veterinary care, behavior training or resources, "safe havens" for animals of abused spouses, or other services.

See also Dog adoption.