Organ donation is generally assumed to require the consent of the donor and, sometimes, their next of kin. This is complicated in cases of posthumous donation, as the donor is no longer able to consent. Most countries allow individuals to specify their wishes before they die, either by joining a donor register (opt-in or explicit consent) or by registering an objection to donation (opt-out, often referred to as “presumed consent”). While this is perhaps the most discussed issue around consent to organ donation, this chapter also discusses the consent of transplant recipients and the relatives of the donor, who may be taken to have their own standing to give or refuse consent.