| Country | Legal system |
| Saudi Arabia | Islamic (sharia) legal system with some elements of Egyptian, French, and customary law; note - several secular codes have been introduced; commercial disputes handled by special committees |
| Senegal | civil law system based on French law; judicial review of legislative acts in Constitutional Court |
| Serbia | civil law system |
| Seychelles | mixed legal system of English common law, French civil law, and customary law |
| Sierra Leone | mixed legal system of English common law and customary law |
| Singapore | English common law |
| Sint Maarten | based on Dutch civil law system with some English common law influence |
| Slovakia | civil law system based on Austro-Hungarian codes; note - legal code modified to comply with the obligations of Organization on Security and Cooperation in Europe and to expunge Marxist-Leninist legal system |
| Slovenia | civil law 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 |
| South Sudan | void |
| 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 |