Embryo donation is a form of third party reproduction. It is defined as the giving—generally without compensation—of embryos remaining after one couple's In vitro fertilisation, or IVF treatments, to another person or couple, followed by the placement of those embryos into the recipient woman's uterus to facilitate pregnancy and childbirth in the recipient. Most often, the embryos are donated after the woman for whom they were originally created has successfully carried one or more pregnancies to term. The resulting child is considered the child of the woman who carries it and gives birth, and not the child of the donor. This is the same principle as is followed in egg donation or sperm donation.

Embryo donation can be handled on an anonymous basis (donor and recipient parties are not known to each other), or on an open basis (parties' identities are shared and the families agree to a relationship. Occasionally, a "semi-open" arrangement is used in which the parties know family and other information about each other, but their real names and locating information are withheld, in order to provide a layer of privacy protection. Some writers use the term "embryo donation" to refer strictly to anonymous embryo donation, and "embryo adoption" to refer to the open process. Others use the terms synonymously because regardless of whether the arrangement is open or anonymous, the donation of embryos and a clinical assisted reproduction procedure is involved, and the recipient couple is preparing to raise a child not genetically related to them.

Those donating embryos must, if possible, be screened for a series of infectious diseases. If the donors are not available to be screened, the embryos must be given a label that indicates that the required screening has not been done, and the recipients must agree to accept the associated risk. The amount of screening the embryo has already undergone is largely dependent on the genetic parents' own IVF clinic and process. The embryo recipient may elect to have her own embryologist conduct further testing. Alternatives to donating remaining embryos are: discarding them (or having them implanted at a time when pregnancy is very unlikely, or donating them for use in embryonic stem cell research. Although embryos can, theoretically, survive indefinitely in frozen storage, as a practical reality someone must eventually decide on a permanent disposition for them.