The Commonwealth of Nations, commonly known as the Commonwealth (formerly the British Commonwealth), is an intergovernmental organisation of 53 member states that were mostly territories of the former British Empire. The Commonwealth operates by intergovernmental consensus of the member states, organised through the Commonwealth Secretariat, and non-governmental organisations, organised through the Commonwealth Foundation.
The Commonwealth dates back to the mid 20th century with the decolonization of the British Empire through increased self-governance of its territories. It was formally constituted by the London Declaration in 1949, which established the member states as "free and equal". The symbol of this free association is Queen Elizabeth II who is the Head of the Commonwealth. The Queen is also the monarch of 16 members of the Commonwealth, known as Commonwealth realms. The other members of the Commonwealth have different persons as head of state: 32 members are republics and five members are monarchies with a different monarch.
Member states have no legal obligation to one another. Instead, they are united by language, history, culture, and their shared values of democracy, human rights, and the rule of law. These values are enshrined in the Commonwealth Charter and promoted by the quadrennial Commonwealth Games. On 3 October 2013, after 48 years of membership, the Gambia became the most recent nation to withdraw from the Commonwealth.
The Commonwealth covers more than 29,958,050 km2 (11,566,870 sq mi), almost a quarter of the world land area, and spans all the continents. With an estimated population of 2.328 billion, near a third of the world population, the Commonwealth in 2012 produced a nominal gross domestic product (GDP) of $10.450 trillion, representing 17% of the world GDP when measured in purchasing power parity (PPP) and 14% of the Gross world product when measured nominally. This represents the second largest nominal GDP and third largest GDP PPP in the world.