Over a century since its development, the analytical technique of mass spectrometry is blooming more than ever, and applied in nearly all aspects of the natural and life sciences. In the last two decades mass spectrometry has also become amenable to the analysis of proteins and even intact protein complexes, and thus begun to make a significant impact in the field of structural biology. In this Review, we describe the emerging role of mass spectrometry, with its different technical facets, in structural biology, focusing especially on structural virology. We describe how mass spectrometry has evolved into a tool that can provide unique structural and functional information about viral‐protein and protein‐complex structure, conformation, assembly, and topology, extending to the direct analysis of intact virus capsids of several million Dalton in mass. Mass spectrometry is now used to address important questions in virology ranging from how viruses assemble to how they interact with their host. Viruses on mass: Structural biology has profited greatly from modern biomolecular mass spectrometry (MS). In this Review a variety of mass spectrometry techniques, including proteomics, H/D exchange, chemical labeling, and native and ion mobility MS, are presented along with how they have contributed to structural‐biology investigations, in particular of virus structure, assembly, and dynamics (see picture).