This essay considers how ancient Stoic cosmopolitanism – roughly, the claim all human beings are members of the same “cosmopolis”, or universal city, and so are entitled to moral concern in virtue of possessing reason – informs Stoic thinking about how we ought to treat non-human entities in the environment. First, I will present the Stoic justification for the thesis that there are only rational members of the cosmopolis – and so that moral concern does not extend to any non-human (...) part of the natural world – and explore the foundations of these views in Stoic physics. Next, I will show that, like other anthropocentric theories, Stoic cosmopolitanism allows for environmental preservation and protection of non-human entities, so long as these activities ultimately benefit human beings. However, because the Stoics include the appreciation of natural beauty as a component of the happy life, this justification is not as feeble as it might seem. Humans are naturally set up to contemplate the order and complexity of the universe, and so environmental degradation and species loss, in marring this harmonious system, frustrates the achievement of the human goal. After exploring these facets of Stoic philosophy, and assessing to what extent they might justify environmental conservation, I close with a critical appraisal of Stoic theory – specifically, of the claims that (i) only humans possess reason and (ii) only rational creatures are deserving of moral concern. (shrink)