| Country | Constitution |
| Spain | approved by legislature 31 October 1978; passed by referendum 6 December 1978, effective 29 December 1978 |
| Spratly Islands | void |
| Sri Lanka | adopted 16 August 1978, certified 31 August 1978 |
| Sudan | constitution implemented on 30 June 1998, partially suspended 12 December 1999 by President BASHIR; under the CPA, Interim National Constitution ratified 5 July 2005; Constitution of Southern Sudan signed December 2005 |
| Suriname | ratified 30 September 1987; effective 30 October 1987 |
| Svalbard | void |
| Swaziland | signed by the King in July 2005 went into effect on 8 February 2006 |
| Sweden | 1 January 1975 |
| Switzerland | revision of Constitution of 1874 approved by the Federal Parliament 18 December 1998, adopted by referendum 18 April 1999, officially entered into force 1 January 2000 |
| Syria | 13 March 1973 |
| Taiwan | 25 December 1947; amended in 1992, 1994, 1997, 1999, 2000, 2005 note: constitution adopted on 25 December 1946; went into effect on 25 December 1947 |
| Tajikistan | 6 November 1994 |
| Tanzania | 25 April 1977; major revisions October 1984 |
| Thailand | constitution signed by King PHUMIPHON (BHUMIBOL) on 24 August 2007 |
| Timor-Leste | 22 March 2002 (based on the Portuguese model) |
| Togo | multiparty draft constitution approved by High Council of the Republic 1 July 1992, adopted by public referendum 27 September 1992 |
| Tokelau | administered under the Tokelau Islands Act of 1948; amended in 1970 |
| Tonga | 4 November 1875; revised 1 January 1967 |
| Trinidad and Tobago | 1 August 1976 |
| Tunisia | 1 June 1959; amended 1988, 2002 |
| Turkey | 7 November 1982 |
| Turkmenistan | adopted 18 May 1992 |
| Turks and Caicos Islands | Turks and Caicos Islands Constitution Order 2006 (effective 9 August 2006) |
| Tuvalu | 1 October 1978 |
| Uganda | 8 October 1995; in 2005 the constitution was amended removing presidential term limits and legalizing a multiparty political system |
| Ukraine | adopted 28 June 1996 |
| United Arab Emirates | 2 December 1971; made permanent in 1996 |
| United Kingdom | unwritten; partly statutes, partly common law and practice |
| United States | 17 September 1787, effective 4 March 1789 |
| United States Pacific Island Wildlife Refuges | void |
| Uruguay | 27 November 1966, effective 15 February 1967; suspended 27 June 1973, new constitution rejected by referendum 30 November 1980; two constitutional reforms approved by plebiscite 26 November 1989 and 7 January 1997 |
| Uzbekistan | adopted 8 December 1992 |
| Vanuatu | 30 July 1980 |
| Venezuela | 30 December 1999 |
| Vietnam | 15 April 1992 |
| Virgin Islands | Revised Organic Act of 22 July 1954 |
| Wake Island | void |
| Wallis and Futuna | 4 October 1958 (French Constitution) |
| West Bank | void |
| Western Sahara | void |
| World | void |
| Yemen | 16 May 1991; amended 29 September 1994 and February 2001 |
| Zambia | 24 August 1991; amended in 1996 to establish presidential term limits |
| Zimbabwe | 21 December 1979 |