| Country | Legal system |
| Solomon Islands |  mixed legal system of English common law and customary law |
| Somalia |  mixed legal system of civil law, Islamic law, and customary law (referred to as Xeer) |
| South Africa |  mixed legal system of Roman-Dutch civil law, English common law, and customary law |
| South Georgia and the South Sandwich Islands | the laws of the UK where applicable apply; the senior magistrate from the Falkland Islands presides over the Magistrates Court |
| Southern Ocean | void |
| Spain |  civil law system with regional variations |
| Spratly Islands | void |
| Sri Lanka |  mixed legal system of Roman-Dutch civil law, English common law, and Jaffna Tamil customary law |
| Sudan |  mixed legal system of Islamic law and English common law in the north, and primarily customary law in the south |
| Suriname |  civil law system influenced by Dutch civil law; note - the Commissie Nieuw Surinaamse Burgerlijk Wetboek completed drafting a new civil code in February 2009 |
| Svalbard | the laws of Norway where applicable apply |
| Swaziland |  mixed legal system of civil, common, and customary law |
| Sweden |  civil law system influenced by Roman-Germanic law and customary law |
| Switzerland |  civil law system; judicial review of legislative acts, except for federal decrees of a general obligatory character |
| Syria |  mixed legal system of civil and Islamic law (for family courts) |
| Taiwan |  civil law system |
| Tajikistan |  civil law system |