| Sergej | | syer-GYAY (Russian), seer-GYAY (Russian) | Russian, Bulgarian | |
| Sergey | | syer-GYAY (Russian), seer-GYAY (Russian) | Russian, Bulgarian | |
| Sevastian | | - | Russian | |
| Sevastyan | | - | Russian | |
| Shekinah | | - | Various | |
| Shura | | - | Russian | |
| Slava | | - | Russian, Slovene, Croatian | |
| Snezhana | | - | Russian, Bulgarian, Macedonian | |
| Sofiya | | sah-FEE-yah (Russian) | Russian, Ukrainian, Bulgarian | |
| Sofya | | - | Russian | |
| Soleil | | so-LAY | Various | |
| Sonya | | SON-yə (English), SAWN-yə (English) | Russian, English | |
| Spartak | | - | Russian, Ukrainian, Bulgarian, Albanian, Armenian, Georgian | |
| Stanimir | | - | Bulgarian, Russian, Serbian, Medieval Slavic | |
| Stanislav | | stah-nee-SLAHF (Russian) | Czech, Slovak, Russian, Ukrainian, Bulgarian, Slovene, Serbian, Croatian, Medieval Slavic | |