 Presentism is the view that only present things exist. So understood, presentism is primarily an ontological doctrine; it’s a view about what exists, absolutely and unrestrictedly. The view is the subject of extensive discussion in the literature on time and change, with much of it focused on the problems that presentism allegedly faces. Thus, most of the literature that frames the development of presentism has grown up either in formulating objections to the view (e.g., Sider 2001: 11–52), or in response to such objections (e.g., Bigelow 1996; Markosian 2004), with exceptions to this largely coming via the ways in which presentism is motivated. This entry mirrors the structure of that literature, for the most part. Here’s the plan for what follows. We begin with a more detailed sketch of presentism, unpacking its commitments and motivations. Then, we move to consider several concerns raised for presentists. We use these to illustrate the breadth and severity of the challenges that presentism faces, as well as the range of different versions of presentism developed to help meet these challenges.