| Country | Constitution |
| Saint Lucia | 22 February 1979 |
| Saint Martin | 4 October 1958 (French Constitution) |
| Saint Pierre and Miquelon | 4 October 1958 (French Constitution) |
| Saint Vincent and the Grenadines | 27 October 1979 |
| Samoa | 1 January 1962 |
| San Marino | 8 October 1600; electoral law of 1926 serves some of the functions of a constitution |
| Sao Tome and Principe | approved March 1990, effective 10 September 1990 |
| Saudi Arabia | governed according to Islamic law; the Basic Law that articulates the government's rights and responsibilities was promulgated by royal decree in 1992 |
| Senegal | adopted 7 January 2001; amended many times |
| Serbia | adopted 8 November 2006; effective 10 November 2006 |
| Seychelles | 18 June 1993 |
| Sierra Leone | 1 October 1991; amended several times |
| Singapore | 3 June 1959; amended 1965 (based on pre-independence State of Singapore Constitution) |
| Sint Maarten | Staatsregeling, 10 October 2010; revised Kingdom Charter pending |
| Slovakia | ratified 1 September 1992, effective 1 January 1993; changed September 1998; amended February 2001 note: the change in September 1998 allowed direct election of the president; the amendment of February 2001 allowed Slovakia to apply for NATO and EU membership |
| Slovenia | adopted 23 December 1991, amended 14 July 1997 and 25 July 2000 |
| Solomon Islands | 7 July 1978 |
| Somalia | 25 August 1979, presidential approval 23 September 1979 note: the formation of transitional governing institutions, known as the Transitional Federal Government, is currently ongoing |
| South Africa | 10 December 1996; note - certified by the Constitutional Court 4 December 1996; was signed by then President MANDELA 10 December 1996; and entered into effect 4 February 1997 |
| South Georgia and the South Sandwich Islands | void |