| 100% | ELBE | 4 | River that formed part of the border between East and West Germany |
| 78% | ODER | 4 | River that forms part of the border between Germany and Poland |
| 78% | MOSELLE | 7 | River that forms part of the border between Germany and Luxembourg |
| 75% | DOURO | 5 | River that forms part of the border between Spain and Portugal before flowing west to the Atlantic |
| 71% | ORINOCO | 7 | River that forms part of the border between Colombia and Venezuela |
| 71% | DOURO | 5 | River that forms part of the border between Spain and Portugal |
| 71% | RIONEGRO | 8 | River that forms part of the border between Colombia and Venezuela |
| 66% | MOSELLE | 7 | River forming part of the border between Germany and Luxembourg |
| 63% | KASAI | 5 | Tributary of the Congo River that forms part of the border between the Democratic Republic of the Congo and Angola |
| 62% | TAMAR | 5 | River that forms most of the border between Cornwall and Devon |
| 60% | ARAS | 4 | River forming part of the border between Azerbaijan and Iran |
| 60% | YALU | 4 | River that forms a large part of the border between North Korea and China |
| 58% | RHINE | 5 | River that forms part of the France/Germany border |
| 56% | SNAKE | 5 | — River, US watercourse forming part of the border between Idaho and Oregon |
| 55% | GUADIANA | 8 | River that forms part of the Spain-Portugal border |
| 55% | WABASH | 6 | River that forms part of the Illinois-Indiana border |
| 54% | NIAGARA | 7 | River that forms part of the U.S.-Canada border |
| 51% | URAL | 4 | River forming part of the boundary between Europe and Asia |
| 48% | DEE | 3 | River that forms part of the England/Wales boundary |
| 47% | MORAVA | 6 | River that forms the border between Slovakia and Austria |
| 47% | MEKONG | 6 | River that forms the border between Laos and Myanmar |
| 47% | MAMORE | 6 | River rising in the Andes that forms part of the Bolivia-Brazil border |
| 45% | IOWA | 4 | The Mississippi and Missouri rivers form parts of its border |
| 45% | MEKONG | 6 | River that forms much of the Laos/Thailand border |
| 43% | EMS | 3 | River forming part of the Germany-Netherlands boundary |
| 43% | AMUR | 4 | River that forms the boundary between Manchuria and Russia |
| 43% | TWRCH | 5 | River that formed the ancient boundary between Brecknockshire and Carmarthenshire |
| 43% | ELBE | 4 | It formed part of East Germany's border |
| 42% | DRINA | 5 | River that forms the boundary between Bosnia and Herzegovina and Montenegro |
| 42% | IOWA | 4 | Its east and west borders are formed entirely by rivers |