| SLF | 0 | United Kingdom | GB-SLF |
| SLG | 0 | United Kingdom | GB-SLG |
| Sliema | 0 | Malta | MT-56 |
| Sliven Province | 0 | Bulgaria | BG-20 |
| SLK | 0 | United Kingdom | GB-SLK |
| Slovenj Gradec City Municipality | 0 | Slovenia | SI-112 |
| Slovenska Bistrica Municipality | 0 | Slovenia | SI-113 |
| Slovenske Konjice Municipality | 0 | Slovenia | SI-114 |
| SM | 0 | Romania | RO-SM |
| Šmarje pri Jelšah Municipality | 0 | Slovenia | SI-124 |
| Šmarješke Toplice Municipality | 0 | Slovenia | SI-206 |
| Šmartno ob Paki Municipality | 0 | Slovenia | SI-125 |
| Šmartno pri Litiji Municipality | 0 | Slovenia | SI-194 |
| Smiltene Municipality | 0 | Latvia | LV-094 |
| SMO | 0 | Russia | RU-SMO |
| Smolyan Province | 0 | Bulgaria | BG-21 |
| SN | 0 | Germany | DE-SN |
| SN | 0 | Moldova | MD-SN |
| SN | 0 | Hungary | HU-SN |
| SND | 0 | United Kingdom | GB-SND |
| SO | 0 | Moldova | MD-SO |
| SO | 0 | Hungary | HU-SO |
| SO | 0 | Spain | ES-SO |
| SO | 0 | Switzerland | CH-SO |
| SO | 0 | Ireland | IE-SO |
| Södermanland County | 0 | Sweden | SE-D |
| Sodražica Municipality | 0 | Slovenia | SI-179 |
| Sofia City Province | 0 | Bulgaria | BG-22 |
| Sofia Province | 0 | Bulgaria | BG-23 |
| Sogn og Fjordane | 0 | Norway | NO-14 |
| Sokolov | 0 | Czech Republic | CZ-413 |
| SOL | 0 | United Kingdom | GB-SOL |
| Solčava Municipality | 0 | Slovenia | SI-180 |
| SOM | 0 | United Kingdom | GB-SOM |
| Sopište Municipality | 0 | Republic of North Macedonia | MK-70 |
| Sør-Trøndelag | 0 | Norway | NO-16 |
| SOS | 0 | United Kingdom | GB-SOS |
| Šoštanj Municipality | 0 | Slovenia | SI-126 |
| South Aegean | 0 | Greece | GR-L |
| South Bačka District | 0 | Serbia | RS-06 |
| South Banat District | 0 | Serbia | RS-04 |
| South Karelia | 0 | Finland | FI-02 |
| South Tyrol | 0 | Italy | IT-BZ |
| Southern Ostrobothnia | 0 | Finland | FI-03 |
| Southern Peninsula Region | 0 | Iceland | IS-2 |
| Southern Region | 0 | Iceland | IS-8 |
| Southern Savonia | 0 | Finland | FI-04 |
| SPE | 0 | Russia | RU-SPE |
| Split-Dalmatia County | 0 | Croatia | HR-17 |
| Središče ob Dravi | 0 | Slovenia | SI-202 |
| Srem District | 0 | Serbia | RS-07 |
| SRY | 0 | United Kingdom | GB-SRY |
| SS | 0 | Hungary | HU-SS |
| ST | 0 | Germany | DE-ST |
| ST | 0 | Moldova | MD-ST |
| ST | 0 | Hungary | HU-ST |
| St. Julian's | 0 | Malta | MT-48 |
| St. Paul's Bay | 0 | Malta | MT-51 |
| STA | 0 | Russia | RU-STA |
| Stara Zagora Province | 0 | Bulgaria | BG-24 |
| Staro Nagoričane Municipality | 0 | Republic of North Macedonia | MK-71 |
| Starše Municipality | 0 | Slovenia | SI-115 |
| STB | 0 | United Kingdom | GB-STB |
| STE | 0 | United Kingdom | GB-STE |
| STG | 0 | United Kingdom | GB-STG |
| STH | 0 | United Kingdom | GB-STH |
| Štip Municipality | 0 | Republic of North Macedonia | MK-83 |
| STN | 0 | United Kingdom | GB-STN |
| Stockholm County | 0 | Sweden | SE-AB |
| Stopiņi Municipality | 0 | Latvia | LV-095 |
| Štore Municipality | 0 | Slovenia | SI-127 |
| Strakonice | 0 | Czech Republic | CZ-316 |
| Straža Municipality | 0 | Slovenia | SI-203 |
| Středočeský kraj | 0 | Czech Republic | CZ-20 |
| Strenči Municipality | 0 | Latvia | LV-096 |
| Struga Municipality | 0 | Republic of North Macedonia | MK-72 |
| Strumica Municipality | 0 | Republic of North Macedonia | MK-73 |
| STS | 0 | United Kingdom | GB-STS |
| STT | 0 | United Kingdom | GB-STT |
| Studeničani Municipality | 0 | Republic of North Macedonia | MK-74 |
| STY | 0 | United Kingdom | GB-STY |
| Styria | 0 | Austria | AT-6 |
| Šumadija District | 0 | Serbia | RS-12 |
| Šumperk | 0 | Czech Republic | CZ-715 |
| Sumy Oblast | 0 | Ukraine | UA-59 |
| Šuto Orizari Municipality | 0 | Republic of North Macedonia | MK-84 |
| SV | 0 | Romania | RO-SV |
| SV | 0 | Moldova | MD-SV |
| Svalbard | 0 | Norway | NO-21 |
| SVE | 0 | Russia | RU-SVE |
| Švenčionys District Municipality | 0 | Lithuania | LT-49 |
| Sveta Ana Municipality | 0 | Slovenia | SI-181 |
| Sveta Trojica v Slovenskih Goricah Municipality | 0 | Slovenia | SI-204 |
| Sveti Andraž v Slovenskih Goricah Municipality | 0 | Slovenia | SI-182 |
| Sveti Jurij ob Ščavnici Municipality | 0 | Slovenia | SI-116 |
| Sveti Jurij v Slovenskih Goricah Municipality | 0 | Slovenia | SI-210 |
| Sveti Nikole Municipality | 0 | Republic of North Macedonia | MK-69 |
| Sveti Tomaž Municipality | 0 | Slovenia | SI-205 |
| Svitavy | 0 | Czech Republic | CZ-533 |
| SWA | 0 | United Kingdom | GB-SWA |
