This article examines the emergence of a human right to a healthy environment emerged; how it is recognized in international, regional, national and subnational legal instruments; the extent to which it has been implemented in law; whether it improves environmental and human health outcomes; and the potential for international recognition. It posits that the case for legal recognition of a RHE is complicated and complex. There are normative, legal, ethical, and moral justifications that both the planet and people living on it are better off in a world that recognizes a RHE. Environmental rights are real. The article reports that there are 136 countries subject to a legal RHE, including: • 84 expressly (see Appendix, The Case for Environmental Human Rights). See also, Environmental Rights Map (same); • 6 reliably impliedly (Bangladesh, Guatemala, India, Pakistan, Panama, and Sri Lanka); • 23 legislatively--not already counted (Armenia, Bhutan, Bosnia-Herzegovina, Cyprus, Djibouti, Eretria, Gambia, Guatemala, Guinea-Bissau, Haiti, Kazakhstan, Lebanon, Liberia, Lithuania, Madagascar, Monaco, Nigeria, Palau, Panama, Saudi Arabia, Tajikistan, Tanzania, and Uruguay); • 23 per ratification of the African Charter--not already counted (see Appendix); Does legal recognition of a RHE improve environmental outcomes? The article reports that with some exceptions there is (still) very modest pursuit of RHE-based legal claims by litigants. Very few cases reach the merits. Few apex courts (those that issue controlling or precedential decisions) engage express RHE-based claims. Those asked to consider whether there is an unenumerated RHE usually find there isn’t. There are complex reasons for the dearth of cases. Many constitutionally entrenched provisions aren’t self-executing (enforceable without legislative action) because they don’t appear in the “fundamental rights” or “bill of rights” portion of the constitution. Even if they do, a gauntlet of procedural obstacles await, including “standing” (who can sue), “jurisdiction” (which court can hear the matter), and separation of powers (whether the matter should be presented to another – perhaps elected – branch of government). There is much more jurisprudence regarding the extent to which other socioeconomic and cultural (“SEC”) rights impliedly incorporate a RHE, including rights life, health, water, family and dignity. Exemplars include the countries noted above, as well as some regional tribunals, including the European and Inter-American Courts of Human Rights. Yet implementation lags even where enforcement succeeds. While embedding a RHE in a constitution may correlate (or be “positively associated”) with better environmental performance (and the results here are mixed), evidence – especially that which has been replicated – that doing so necessarily causes environmental improvement is in short supply. Presently, there is more evidence of effectiveness in vindicating SEC rights in the service of environmental improvement, including concerning climate change. A fair assessment is that while the case for RHE is solid, it has shortcomings that warrant further evidence-based analytical interrogation and judicial training. In the end, the outcome and objective converge: the world is better off for recognizing everyone’s right to a healthy environment. International recognition can help to redress shortcomings, realize potential, and catalyze the cause. [End]