In agriculture and in the hobby of animal fancy, a breeder is an individual animal used for selective breeding.

If the breeding is for a purebred animal it must be registered and must conform to the criteria laid out for that breed. In addition, the breed club or governing authority may have other restrictions on the type of animal that can be used for breeding.

For example, some equine societies allow backbred and crossbred individuals to be bred from; most dog clubs do not except in exceptional circumstances, by permission. Most kennel clubs allow any registered individual to be bred from; the individual breed club may have additional, stricter criteria. The Mini Foxie Club of Australia, Inc., for example, requires adult dogs to be classified before being certified eligible for breeding of purebred Miniature Fox Terriers. Some Jack Russell Terrier and Greater Swiss Mountain Dog clubs have similar requirements.

In animal fancy, human breeders have specialized words for breeding animals in some species:  :Please list only if different for the words for the male and female of the species.

• Cat: Stud (male) and Queen (female)
• Dog: Stud (male) and Brood Bitch (female)

These should not be confused with the words for the parents of offspring (i.e. sire and dam) or with the words for male and female of the species (i.e. dog and bitch).