When facts are proven within the formal process of legal proof, in virtue of what are they proven? This deceptively simple question is both a matter of enormous practical importance and a matter of intense, ongoing dispute within evidence scholarship. A conventional story purports to answer this question in terms of probabilistic facts (or, alternatively, in terms of beliefs about probabilistic facts). An alternative to this conventional story answers this question in terms of explanatory facts (facts about the relationships between possible explanations, evidence, and disputed events). This article examines legal proof, and the debates in legal scholarship, through the lens of “grounding.” In employing this perspective, one asks: in virtue of what are facts proven within legal proof? Another way of asking this question is to ask: what grounds the fact that a disputed fact is proven, when it is proven? This article argues for a general thesis and a specific thesis. The general thesis is that the philosophical literature on grounding provides a useful analytical framework for understanding both legal proof and the ongoing debates in legal scholarship. The specific thesis is that when facts are proven within the process of legal proof, they are proven in virtue of various explanatory facts. The article concludes by discussing some of the implications of the analysis for philosophers analyzing the epistemology of legal proof.