Although, in many countries, the military is the most trusted state institution, we know little about public trust in the military outside the United States. We argue that, for the military, trust is grounded in its legitimation as, and aspiration to be, non-partisan. From this insight, we develop hypotheses regarding the relationship between trust in the military and other institutions, the military’s centrality to political power, intrastate conflict, and recruitment format. Using cross-national data (2006–2021), we find support for these hypotheses. Falling trust in partisan state institutions benefits the armed forces. When the military exercises influence over politics, at odds with its legitimation, it is judged by the usual standards of government performance. Civil wars convert the military into a factional actor, and public trust falls. When militaries recruit via selective conscription, confidence suffers. These findings have important implications for civil-military relations, military effectiveness, and democratic stability.