Rivers are commonly used to define political borders, but no global study has quantified the importance of rivers on territorial delimitation at subnational scales. This paper presents Global Subnational River-Borders (GSRB), a first comprehensive geospatial dataset of subnational, as well as national, political borders set by large rivers. GSRB incorporates three previous vector datasets (GAUL, GRWL + +, and WDBII) to map and quantify the use of large rivers as political borders at local, state, and national scales. GSRB conservatively finds that at least 58,588 km (23%) of the world's interior (non-coastal) national borders, 199,922 km (17%) of the world's interior state/province borders, and 459,459 km (12%) of the world's interior local-level political borders are set by large rivers. GSRB finds 222, 2,350, and 14,808 dyads sharing river-borders at these three administrative scales, respectively. While previous studies have emphasized transboundary rivers separating nations, GSRB highlights the abundance of river-borders at subnational scales, where numerous domestic stakeholders share jurisdiction in water resource management. These participants, identified with GSRB, ought not to be ignored when crafting water policy and instituting whole-basin management regimes. GSRB should prove useful for global, geospatial analyses of riparian stakeholders across administrative scales. The GSRB dataset (DOI: 10.5281/zenodo.3906566) can be found via the following link https://zenodo.org/record/3906567#.XvN-GGhKjIU.

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