| Country | Military - note |
| Puerto Rico | defense is the responsibility of the US |
| Qatar | void |
| Romania | void |
| Russia | void |
| Rwanda | void |
| Saint Barthelemy | defense is the responsibility of France |
| Saint Helena | defense is the responsibility of the UK |
| Saint Kitts and Nevis | void |
| Saint Lucia | void |
| Saint Martin | defense is the responsibility of France |
| Saint Pierre and Miquelon | defense is the responsibility of France |
| Saint Vincent and the Grenadines | void |
| Samoa | Samoa has no formal defense structure or regular armed forces; informal defense ties exist with NZ, which is required to consider any Samoan request for assistance under the 1962 Treaty of Friendship |
| San Marino | defense is the responsibility of Italy |
| Sao Tome and Principe | Sao Tome and Principe's army is a tiny force with almost no resources at its disposal and would be wholly ineffective operating unilaterally; infantry equipment is considered simple to operate and maintain but may require refurbishment or replacement after 25 years in tropical climates; poor pay, working conditions, and alleged nepotism in the promotion of officers have been problems in the past, as reflected in the 1995 and 2003 coups; these issues are being addressed with foreign assistance aimed at improving the army and its focus on realistic security concerns; command is exercised from the president, through the Minister of Defense, to the Chief of the Armed Forces staff (2005) |
| Saudi Arabia | void |
| Senegal | void |
| Serbia | void |
| Seychelles | void |
| Sierra Leone | void |
| Singapore | void |
| Slovakia | void |
| Slovenia | void |
| Solomon Islands | void |
| Somalia | void |
| South Africa | with the end of apartheid and the establishment of majority rule, former military, black homelands forces, and ex-opposition forces were integrated into the South African National Defense Force (SANDF); as of 2003 the integration process was considered complete |
| South Georgia and the South Sandwich Islands | defense is the responsibility of the UK |
| Southern Ocean | void |
| Spain | void |
| Spratly Islands | Spratly Islands consist of more than 100 small islands or reefs of which about 45 are claimed and occupied by China, Malaysia, the Philippines, Taiwan, and Vietnam |
| Sri Lanka | void |
| Sudan | void |
| Suriname | void |
| Svalbard | Svalbard is a territory of Norway, demilitarized by treaty on 9 February 1920 |
| Swaziland | void |
| Sweden | void |
| Switzerland | void |
| Syria | void |