The pot-bellied pig (Vietnamese: Lợn ỉn) is a breed of domesticated pig originating in Vietnam with fourteen sub-species. Considerably smaller than standard American or European farm pigs, most adult pot-bellied pigs are about the size of a medium- or large-breed dog, though their bodies are denser at a weight of 27 to 136 kg (60 to 300 lb). Pot-bellied pigs can be easily discerned from other pig breeds by their size, upright ears and straight tail. Pigs with fat rolls over their eyes or a belly that touches the ground are easy visual indicators that the pig is overweight. Although they have a pot belly and a swayed back, these are not indicative of weight. Pigs in proper weight still have the sway and belly, but the hip bones can easily be felt with minimal pressure and the eyes (whole socket) should be easily visible.

Because pot-bellied pigs are in the same species as ordinary farmyard pigs and wild boars, they are capable of interbreeding. The Swedish Agriculture Ministry has been assisting Vietnam with its pork production by introducing large breeds of pigs into Vietnam since the mid-1980s.

Pot-bellied pig that is not within the proper weight range. Today, the Vietnamese and Swedish governments have realized that the indigenous Vietnamese pig sub-species exist only in mountainous Vietnam and Thailand. The Vietnamese government has begun to subsidize local farmers that continue to raise the indigenous pot-bellied pigs because it realizes they are neither as prolific nor as large as other breeds.

Boars, un-neutered male pigs, become fertile at a young age, long before they are completely physically mature. Pot-bellied pigs are considered fully grown by six years of age, when the epiphyseal plates in their spines finally close.