| Country | Constitution |
| Bangladesh | 4 November 1972; effective 16 December 1972; suspended following coup of 24 March 1982; restored 10 November 1986; amended many times |
| Barbados | 30 November 1966 |
| Belarus | 15 March 1994; revised by national referendum of 24 November 1996 giving the presidency greatly expanded powers and became effective 27 November 1996; revised again 17 October 2004 removing presidential term limits |
| Belgium | 7 February 1831; amended many times; revised 14 July 1993 to create a federal state |
| Belize | 21 September 1981 |
| Benin | adopted by referendum 2 December 1990 |
| Bermuda | 8 June 1968; amended 1989 and 2003 |
| Bhutan | ratified 18 July 2008 |
| Bolivia | 2 February 1967; revised in August 1994; voters approved a new constitution on 25 January 2009 |
| Bosnia and Herzegovina | the Dayton Peace Accords, signed 14 December 1995 in Paris, included a new constitution now in force; note - each of the entities also has its own constitution |
| Botswana | March 1965; effective 30 September 1966 |
| Bouvet Island | void |
| Brazil | 5 October 1988 |
| British Indian Ocean Territory | void |
| British Virgin Islands | 13 June 2007 |
| Brunei | 29 September 1959 (some provisions suspended under a State of Emergency since December 1962, others since independence on 1 January 1984) |
| Bulgaria | adopted 12 July 1991 |
| Burkina Faso | approved by referendum 2 June 1991; formally adopted 11 June 1991; last amended January 2002 |
| Burma | 3 January 1974; suspended since 18 September 1988; a new constitution was approved on 10 May 2008; note - new constitution will take effect when a new parliament is convened following elections scheduled for 2010 |
| Burundi | ratified by popular referendum 28 February 2005 |