| 100% | KASAI | 5 | Tributary of the Congo River that forms part of the border between the Democratic Republic of the Congo and Angola |
| 58% | ODER | 4 | River that forms part of the border between Germany and Poland |
| 58% | ORINOCO | 7 | River that forms part of the border between Colombia and Venezuela |
| 58% | MOSELLE | 7 | River that forms part of the border between Germany and Luxembourg |
| 58% | DOURO | 5 | River that forms part of the border between Spain and Portugal |
| 58% | RIONEGRO | 8 | River that forms part of the border between Colombia and Venezuela |
| 58% | ELBE | 4 | River that formed part of the border between East and West Germany |
| 56% | DOURO | 5 | River that forms part of the border between Spain and Portugal before flowing west to the Atlantic |
| 51% | TAMAR | 5 | River that forms most of the border between Cornwall and Devon |
| 50% | YALU | 4 | River that forms a large part of the border between North Korea and China |
| 50% | ARAS | 4 | River forming part of the border between Azerbaijan and Iran |
| 50% | MOSELLE | 7 | River forming part of the border between Germany and Luxembourg |
| 49% | SNAKE | 5 | — River, US watercourse forming part of the border between Idaho and Oregon |
| 47% | BUG | 3 | Tributary of the Narew River forming part of Poland's border with Belarus and Ukraine |
| 47% | BUG | 3 | Tributary of the Narew River forming part of Poland's border with both Belarus and Ukraine |
| 45% | GUADIANA | 8 | River that forms part of the Spain-Portugal border |
| 45% | RHINE | 5 | River that forms part of the France/Germany border |
| 45% | WABASH | 6 | River that forms part of the Illinois-Indiana border |
| 45% | NIAGARA | 7 | River that forms part of the U.S.-Canada border |
| 43% | URAL | 4 | River forming part of the boundary between Europe and Asia |
| 42% | MAMORE | 6 | River rising in the Andes that forms part of the Bolivia-Brazil border |
| 41% | ARUWIMI | 7 | River in NE Democratic Republic of the Congo that rises near Lake Albert as the Ituri |
| 41% | ARUWIMI | 7 | River in northeast Democratic Republic of the Congo that rises near Lake Albert as the Ituri |
| 41% | MORAVA | 6 | River that forms the border between Slovakia and Austria |
| 41% | MEKONG | 6 | River that forms the border between Laos and Myanmar |
| 39% | DEE | 3 | River that forms part of the England/Wales boundary |
| 39% | ZAIRE | 5 | Country name that replaced (and was later replaced by) Democratic Republic of the Congo |
| 39% | IOWA | 4 | The Mississippi and Missouri rivers form parts of its border |
| 39% | ARUWIMI | 7 | River in the NE Democratic Republic of Congo that rises near Lake Albert as the Ituri |
| 38% | EURASIAN | 8 | Like the Ural Mountains, which form part of the border between two continents |