| Country | Constitution |
| Ireland | adopted 1 July 1937 by plebiscite; effective 29 December 1937 |
| Isle of Man | unwritten; note - The Isle of Man Constitution Act of 1961 does not embody the unwritten Manx Constitution |
| Israel | no formal constitution; some of the functions of a constitution are filled by the Declaration of Establishment (1948), the Basic Laws of the parliament (Knesset), and the Israeli citizenship law; note - since May 2003 the Constitution, Law, and Justice Committee of the Knesset has been working on a draft constitution |
| Italy | passed 11 December 1947, effective 1 January 1948; amended many times |
| Jamaica | 6 August 1962 |
| Jan Mayen | void |
| Japan | 3 May 1947 |
| Jersey | unwritten; partly statutes, partly common law and practice |
| Jordan | 1 January 1952; amended many times |
| Kazakhstan | first post-independence constitution adopted 28 January 1993; new constitution adopted by national referendum 30 August 1995 |
| Kenya | 27 August 2010; the new constitution abolishes the position of prime minister and establishes a bicameral legislature; many details have yet to be finalized and will require significant legislative action |
| Kiribati | 12 July 1979 |
| Korea, North | adopted 1948; revised several times most recently in 2009 |
| Korea, South | 17 July 1948; note - amended or rewritten many times; current constitution approved 29 October 1987 |
| Kosovo | adopted by the Kosovo Assembly 9 April 2008; effective 15 June 2008 |
| Kuwait | approved and promulgated 11 November 1962 |
| Kyrgyzstan | 27 June 2010 |
| Laos | promulgated 14 August 1991; amended in 2003 |
| Latvia | 15 February 1922; restored to force by the Constitutional Law of the Republic of Latvia adopted by the Supreme Council 21 August 1991; multiple amendments since |
| Lebanon | 23 May 1926; amended a number of times, most recently in 1990 to include changes necessitated by the Charter of Lebanese National Reconciliation (Ta'if Accord) of October 1989 |