A surrogate mother or ersatz mother is a woman who carries a child for a couple or single person with the intention of giving that child up once it is born (also called surrogate pregnancy). The surrogate mother may be the baby's biological mother (traditional surrogacy) or she may be implanted with someone else's fertilized egg (gestational surrogacy). The most common reason for using a surrogate mother is infertility. Gay male couples have also used surrogate mothers in order to have children that at least one partner is biologically related to.

It is estimated that in the United States, the payment for a surrogate mother ranges between US$28,000 and $45,000 (?). Gestational surrogacy costs more than traditional surrogacy, since more complicated medical procedures are required.

The most famous case of surrogacy was the Baby M case, in which the surrogate mother refused to surrender the child she had borne to the child's biological father. The Supreme Court of New Jersey awarded custody to the biological father and visitation rights to the surrogate mother.