I have been speaking of the vast regions and varied peoples to whom I owe my duty. But there has also sprung from our island home, a theme of social and political thought, which constitutes our message to the world and ... has found acceptance both within and far beyond my realms.

About 2.5 billion people - out of a global population of eight billion - live in the 56 Commonwealth countries, a global association that serves as a crown society. The Commonwealth also constitutes a quarter of the world's land mass. The largest country by population is India, which represents about half of the total. Following India, Pakistan, Nigeria, and Bangladesh are the next largest countries by population, with the UK coming in fifth. Some of these countries were part of the British Empire, some remain British dominions, while others, having no colonial ties to Britain, have chosen to join the society of the crown.

Fifteen member states recognize King Charles III as their Head of State, while five countries—Lesotho, Eswatini (formerly known as Swaziland), Brunei Darussalam, Malaysia, and Tonga—have their own monarchs. Additionally, 36 nations operate as republics.

Notably, some member states were never part of the British Empire. Rwanda and Mozambique in Africa joined the Commonwealth in 2009 and 1995, respectively, despite not being colonized by Britain. Rwanda had its own reigning King until 1962 and was previously governed by Germany and later Belgium until independence.

The Commonwealth has also seen some members depart over the years. South Africa withdrew in 1961 following criticism from Commonwealth members regarding its apartheid policies, only to rejoin in 1994. Pakistan faced expulsion after a military coup in 1999 but was readmitted in 2004, although its membership faced suspension again between 2007 and 2008. Former Zimbabwean president Robert Mugabe withdrew his country in 2003 after its membership was suspended due to election rigging allegations; Zimbabwe applied for re-admission in 2018, but no decision has been reached. The Maldives was the last country to leave in 2016, returning to the fold in 2020.

The modern Commonwealth was established in 1949 when "British" was removed from its name and allegiance to the Crown was no longer a requirement.

Three individuals have served as heads of the Commonwealth: King George VI, Queen Elizabeth II, and currently, King Charles III. While this position is not hereditary, the society of the crown accepted King Charles as its head in 2018 when he held the title of Prince of Wales.