Catechism number 2296

Organ transplants are in conformity with the moral law if the physical and psychological dangers and risks incurred by the donor are proportionate to the good sought for the recipient. Donation of organs after death is a noble and meritorious act and is to be encouraged as a manifestation of generous solidarity. It is not morally acceptable if the donor or those who legitimately speak for him have not given their explicit consent.
It is furthermore morally inadmissible directly to bring about the disabling mutilation or death of a human being, even in order to delay the death of other persons.

Respect for bodily integrity