Although human well-being is a topic of much contemporary philosophical discussion, there has been comparatively little theoretical discussion in philosophy of (nonhuman) animal well-being. Animal welfare science is a well-established scientific discipline that studies animal well-being from an empirical standpoint. This article examines parts of this literature that may be relevant to philosophical treatments of animal well-being and to other philosophical issues. First, I explain the dominant conceptions of well-being in animal welfare science and survey some debates in that literature (...) surrounding these competing conceptions. Second, I explain the empirical methods used to measure animal well-being. Third, I argue for the philosophical relevance of the research in animal welfare science and outline some philosophical issues concerning animal welfare and its science that I claim are worthy of attention by philosophers. (shrink)