Xenotransplantation (xeno- from t.he Greek meaning "foreign") is the transplantation of living cells, tissues or organs from one species to another such as from pigs to humans (see Medical grafting) Such cells, tissues or organs are called xenografts or xenotransplants. The term allotransplantation refers to a same-species transplant. Human xenotransplantation offers a potential treatment for end-stage organ failure, a significant health problem in parts of the industrialized world. It also raises many novel medical, legal and ethical issues. A continuing concern is that pigs have different lifespans than humans and their tissues age at a different rate. Disease transmission (xenozoonosis) and permanent alteration to the genetic code of animals are also a cause for concern.

Because there is a worldwide shortage of organs for clinical implantation, about 60% of patients awaiting replacement organs die on the waiting list. Recent advances in understanding the mechanisms of transplant organ rejection have brought science to a stage where it is reasonable to consider that organs from other species, probably pigs, may soon be engineered to minimize the risk of serious rejection and used as an alternative to human tissues, possibly ending organ shortages.

Other procedures, some of which are being carefully investigated in early clinical trials, aim to use cells or tissues from other species to treat life-threatening and debilitating illnesses such as cancer, diabetes, liver failure and Parkinson's disease. If vitrification can be perfected it could allow for long-term storage of xenogenic cells, tissues and organs so they would be more readily available for transplant.

There are only a few published successful xenotransplant procedures.

Xenotransplants are transplants of organs from one species to another, such as an animal organ to humans. They are cutting edge of medical science and could save thousands of people’s lives who are waiting for an organ donation. The animal organ, probably from a pig or baboon could be genetically altered with human genes to trick a patient’s immune system into accepting it as apart of its own body. They have re-emerged because of the lack of organs available and the constant battle to keep immune systems from rejecting the organs. Xenotransplants are thus hopefully able to provide a way of transplants which are safe and effective.