word | | Constitution |
| October | Niue | 19 October 1974 (Niue Constitution Act) |
| October | Pakistan | 12 April 1973; suspended 5 July 1977, restored 30 December 1985; suspended 15 October 1999, restored in stages in 2002; amended 31 December 2003; suspended 3 November 2007; restored on 15 December ... |
| October | Panama | 11 October 1972; major reforms adopted 1978, 1983, 1994, and 2004 |
| October | Poland | adopted by the National Assembly 2 April 1997; passed by national referendum 25 May 1997; effective 17 October 1997 |
| October | Romania | 8 December 1991; revision effective 29 October 2003 |
| October | Saint Barthelemy | 4 October 1958 (French Constitution) |
| October | Saint Martin | 4 October 1958 (French Constitution) |
| October | Saint Pierre and Miquelon | 4 October 1958 (French Constitution) |
| October | Saint Vincent and the Grenadines | 27 October 1979 |
| October | San Marino | 8 October 1600; electoral law of 1926 serves some of the functions of a constitution |
| October | Sierra Leone | 1 October 1991; subsequently amended several times |
| October | Spain | approved by legislature 31 October 1978; passed by referendum 6 December 1978, effective 29 December 1978 |
| October | Suriname | ratified 30 September 1987; effective 30 October 1987 |
| October | Tanzania | 25 April 1977; major revisions October 1984 |
| October | Tuvalu | 1 October 1978 |
| October | Uganda | 8 October 1995; in 2005 the constitution was amended removing presidential term limits and legalizing a multiparty political system |
| October | Wallis and Futuna | 4 October 1958 (French Constitution) |
| officially | 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 |
| old | Moldova | new constitution adopted 29 July 1994, effective 27 August 1994; replaced old Soviet constitution of 1979 |
| Omani | Oman | ... the royal succession, provides for a prime minister, bars ministers from holding interests in companies doing business with the government, establishes a bicameral legislature, and guarantees basic civil liberties for Omani citizens |
| ombudsman | Cape Verde | 25 September 1992; a major revision on 23 November 1995 substantially increased the powers of the president; a 1999 revision created the position of national ombudsman (Provedor de Justica) |
| ongoing | 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 |
| opposition | Kyrgyzstan | ... the expense of the legislature; during large-scale demonstrations in November 2006, President BAKIYEV and the opposition negotiated a new constitution granting greater powers to the parliament and the government; amendments added ... |
| Order | Akrotiri | Sovereign Base Areas of Akrotiri and Dhekelia Order in Council 1960, effective 16 August 1960, functions as a basic legal document |
| Order | Anguilla | Anguilla Constitutional Order 1 April 1982; amended 1990 |
| Order | Dhekelia | Sovereign Base Areas of Akrotiri and Dhekelia Order in Council 1960, effective 16 August 1960, functions as a basic legal document |
| Order | Turks and Caicos Islands | Turks and Caicos Islands Constitution Order 2006 (effective 9 August 2006) |
| Ordinance | Pitcairn Islands | 30 November 1838; reformed 1904 with additional reforms in 1940; further refined by the Local Government Ordinance of 1964 |