This thesis is a systematic investigation of whether there might be conceptual room for the idea that the world itself might be vague, independently of how we describe it. This idea – the existence of so-called ontic vagueness – has generally been extremely unpopular in the literature; my thesis thus seeks to evaluate whether this ‘negative press’ is justified. I start by giving a working definition and semantics for ontic vagueness, and then attempt to show that there are no conclusive arguments that rule out vagueness of this kind. I subsequently establish what type of arguments I think would be most effective in establishing ontic vagueness and provide some arguments of this form. I then highlight a potential worry for this type of argument, but argue that it can be circumvented. Finally, I consider the main ways that the opponent of ontic vagueness would be likely resist the arguments I have offered, and argue that these strategies of response are methodologically problematic. I conclude by claiming that ontic vagueness is a perfectly plausible ontological commitment.