Public goods are goods or services that are open to use by all members of society if they are provided at all. Public goods are both non-excludable and non-rivalrous, i.e. they are goods no society member can be excluded from consuming if they are at all supplied, and for which consumption by one member does not reduce the quantity available to others. Global public goods are public goods for which the pool of beneficiaries spans the entire globe. And intergenerational global public goods, in turn, are global public goods for which the pool of beneficiaries spans multiple generations. An example of an intergenerational global public good is protection from existential risk.