A constitutional convention is a gathering of delegates for the purpose of writing a new constitution or revising an existing constitution. A general constitutional convention is called to create the first constitution of a political unit or to entirely replace an existing constitution. An unlimited constitutional convention is called to revise an existing constitution to the extent that it deems to be proper, whereas a limited constitutional convention is restricted to revising only the areas of the current constitution named in the convention's call, the legal mandate establishing the convention. In the case of the Philadelphia Convention, delegates met for the "sole purpose of revising the Articles of Confederation." George Washington was elected president of this convention. Once the body convened, meeting and deliberations were conducted in secrecy with James Madison serving as recorder. It was rapidly decided that the body would ignore the limitations of its call and propose the replacement of the Articles with an entirely new basic instrument of government.

Examples of constitutional conventions include the:

• United States: Annapolis Convention (1786), which proposed what became the Philadelphia Convention (1787) - Drafted the United States Constitution for ratification by the states. Article V of the constitution sets forth a mechanism whereby future constitutional conventions can be held. The constitution has been amended several times since the Philadelphia Convention, but never (as of 2007) by this method.
• Missouri Constitutional Convention (1861-63), established Missouri's provisional government during the American Civil War
• Canada: (1864), Quebec Conference, 1864, and London Conference of 1866 (1866).
• Australian constitutional conventions - 1891, 1897, 1973 and 1998.
• Germany: Parlamentarischer Rat (Parliamentary Council) (1948) - Drafted the Basic Law of the Federal Republic for ratification by the Länder.
• Northern Ireland Constitutional Convention (1975-1976) - a failed attempt to find a solution to the status of Northern Ireland.
• Scottish Constitutional Convention (1989) - produced a plan for Scottish devolution.
• European Convention (2001) - Drafted the Constitution for Europe for approval by the European Council and ratification by the member states.
• Philippine Constitutional Convention
• 1935 - to draft a constitution to create the autonomous Commonwealth of the Philippines under the U.S. Tydings-McDuffie Act. The constitution was also used in the 3rd Republic (1946) until the passage of the 1973 constitution. Members were elected through the Philippine Constitutional Convention election, 1934
• 1971 - to draft a revised constitution to replace the old U.S. customed 1935 Philippine constititution. Members were elected through the Philippine Constitutional Convention election, 1970. The system of government changed from Presidentitial to Parliamentary to Presidentital-Parliamentary (in 1984 amendment). The constitution lasted until the downfall of Ferdinand Marcos in 1986 and Corazon Aquino appointed members to draft the 1987 Constitution through a Constitutional Commission.

Constitutional conventions have also been used by subnational units of federal states — such as the individual states of the United States — to create, replace, or revise their own constitutions. The 21st Amendment to the US Constitution was also ratified not by the state legislatures, but by state level conventions, as described as an alternate method of ratification in Article V of the US Constitution.