The concept of “commons” is complex; it may relate to property regimes, rules of use and access, recognition of collective importance, or a mixture of these. This paper explores the arguments—developed by a growing epistemic community—to promote mountains as global common goods within the third category. This process may be viewed as starting with the UN Conference on Environment and Development (UNCED) in 1992, and continuing, in particular, through the International Year of Mountains 2002. It has been supported and advanced by focused publications, the establishment of global networks, and advances in technology. Specific arguments state that mountains are important because they provide ecosystem services that are vulnerable to climate change, are home to a significant part of humanity, including many who are disadvantaged, and are centers of cultural, religious, and ethnic diversity. Nevertheless, this proposal has been contested within the scientific community, and the implications for mountain people remain to be discussed.