Municipalities
| Municipality | Population (2025) | km² | per km² |
|---|---|---|---|
| Santander ★ | 175,425 | 37.9 | 4,629 |
| Torrelavega | 51,796 | 35.4 | 1,463 |
| Castro-Urdiales ★ | 33,450 | 97.2 | 344 |
| Camargo | 30,577 | 37.5 | 815 |
| Piélagos | 26,901 | 85.0 | 316 |
| El Astillero | 18,448 | 5.7 | 3,236 |
| Santa Cruz de Bezana | 13,904 | 16.5 | 843 |
| Los Corrales de Buelna | 10,958 | 45.9 | 239 |
| Santoña | 10,835 | 11.1 | 976 |
| Laredo | 10,698 | 15.4 | 695 |
| Santa María de Cayón | 9,538 | 48.1 | 198 |
| Suances | 9,034 | 21.1 | 428 |
| Colindres | 8,570 | 4.9 | 1,749 |
| Reinosa | 8,570 | – | – |
| Reocín | 8,389 | 30.8 | 272 |
| Cabezón de la Sal | 8,226 | 33.0 | 249 |
| Medio Cudeyo | 7,775 | 26.0 | 299 |
| Polanco | 6,304 | 17.8 | 354 |
| Cartes | 5,874 | 18.4 | 319 |
| Entrambasaguas | 5,693 | 42.5 | 134 |
| Miengo | 5,265 | 24.7 | 213 |
| Marina de Cudeyo | 5,221 | 28.0 | 186 |
★ = municipality with a dedicated guide. Municipalities with at least 5,000 inhabitants are listed.