The Alpaca (Vicugna pacos) is a domesticated species of South American camelid. It resembles a small llama in superficial appearance.

Alpacas are kept in herds that graze on the level heights of the Andes of Ecuador, southern Peru, northern Bolivia, and northern Chile at an altitude of 3,500 m (11,483 ft) to 5,000 m (16,404 ft) meters above sea-level, throughout the year. Alpacas are considerably smaller than llamas, and unlike llamas, alpacas were not bred to be beasts of burden but were bred specifically for their fiber. Alpaca fiber is used for making knitted and woven items, much as sheep's wool is. These items include blankets, sweaters, hats, gloves, scarves, a wide variety of textiles and ponchos in South America, and sweaters, socks, coats and bedding in other parts of the world. The fiber comes in more than 52 natural colors as classified in Peru, 12 as classified in Australia and 16 as classified in the United States. Alpacas and llamas differ in that alpacas have straight ears and llamas have banana-shaped ears. Aside from these differences, llamas are on average 1-2 feet taller and proportionally bigger than alpacas.

In the textile industry, "alpaca" primarily refers to the hair of Peruvian alpacas, but more broadly it refers to a style of fabric originally made from alpaca hair but now often made from similar fibers, such as mohair, Icelandic sheep wool, or even high-quality English wool. In trade, distinctions are made between alpacas and the several styles of mohair and luster.

Alpacas have been domesticated for thousands of years. In fact, the Moche people of Northern Peru often used alpaca images in their art. There are no wild alpacas. The closest living species are the wild vicuña, also native to South America, which is believed to be the wild ancestor of the alpaca. Along with camels and llamas, the alpaca are classified as camelids. The alpaca is larger than the vicuña but smaller than the other camelid species. Of the various camelid species, the alpaca and vicuña are the most valuable fiber-bearing animals: the alpaca because of the quality and quantity of its fiber, and the vicuña because of the softness, fineness and quality of its coat. Alpacas are too small to be used as pack animals.

Not all alpacas spit, but all are capable of doing so. "Spit is somewhat euphemistic; occasionally the projectile contains only air and a little saliva but alpacas commonly bring up acidic stomach contents (generally a green grassy mix) and project it onto their chosen target. Spitting is mostly reserved for other alpacas, but an alpaca will occasionally spit at humans that, for example, take away food.

For alpacas, spitting results in what is called "sour mouth." Sour mouth is characterized by a loose-hanging lower lip and a gaping mouth. This is caused by the stomach acids and unpleasant taste of the contents as they pass out of the mouth. Some alpacas will spit when looked at, others will never spit-their personalities are very individualized and there is no hard and fast rule in terms of social behavior, although there is often a group leader, and a group trailer/runt that is picked on by others.

Once they know their owners and feel confident around them, alpacas may allow their backs and necks to be touched. They do not like being grabbed. Once socialized well, some alpacas tolerate being stroked or petted anywhere on their bodies, although many do not like their feet, lower legs, and especially their abdomen touched or handled. If an owner needs to catch an alpaca, the neck offers a good handle -holding the neck firmly between the arms is the best way to restrain the animal. Holding the neck from the rear with the animal's head under one's arm is also very effective.

Alpaca fleece is the natural fiber harvested from an Alpaca. It is light weight or heavy weight, depending on how it is spun, soft, durable, luxurious and silky natural fiber. While similar to sheep's wool, it is warmer, not prickly, and has no lanolin which makes it hypoallergenic. However, this lack of lanolin also prevents Alpaca fiber from being naturally water-repellent. It also has less crimp, thus making it much less elastic. Alpaca fleece is made into various exports, from very simple and inexpensive garments made by the aboriginal communities to sophisticated, industrially made and expensive products such as suits. In the United States, groups of smaller alpaca breeders have banded together to create "fiber co-ops," in order to make the manufacture of alpaca fiber products less expensive.

In physical structure, alpaca fiber is somewhat akin to hair, being very glossy. Alpaca fiber is generally coarser than wool fiber, and alpaca yarns are weaker than most wool yarns. In processing, slivers lack fiber cohesion and single alpaca rovings lack strength. More twisting is necessary to improve strength, but this reduces yarn softness.