Regulatory bundling consists of the ability of administrative agencies to aggregate and disaggregate rules. Agencies, in other words, can bundle what would otherwise be multiple rules into just one. Conversely, they can split one rule into several. This observation parallels other recent work on how agencies can aggregate adjudications and enforcement actions, but now focuses on the most consequential form of agency action: legislative rules. The topic is timely in light of a recent executive order directing agencies to repeal two regulations for every new one promulgated. Agencies now have a greater incentive to pack regulatory provisions together for every two rules they can repeal.This Article explores the positive determinants and normative implications of regulatory bundling. The empirical analysis reveals that agencies have been increasingly engaging in regulatory bundling for the last two decades. More generally, bundling behavior varies widely across different administrative agencies, and agencies appear to include more subjects in their final, as opposed to proposed, rules. These findings, in turn, raise significant normative concerns that could be addressed through a suite of tools novel to the administrative state: single-subject rules, line-item vetoes, and innovative uses of more traditional doctrines of judicial review. Whether some of these tools should be adopted, however, requires further empirical assessment of regulatory bundling’s causes and consequences.