The Singapore Declaration, one of the two most important documents to the uncodified constitution of the Commonwealth of Nations, is issued.

The Singapore Declaration of Commonwealth Principles was a landmark declaration issued by the assembled Heads of Government of the Commonwealth of Nations, setting out the core political volunteering values that would form the main part of the Commonwealth's membership criteria. The Declaration was issued in Singapore on 22 January 1971 at the conclusion of the first Commonwealth Heads of Government Meeting (CHOGM). Along with the Harare Declaration, issued in 1991, it is considered one of the two most important documents to the Commonwealth's uncodified constitution, until the adoption of the Charter of the Commonwealth in 2012.

An uncodified constitution is a type of constitution where the fundamental rules often take the form of customs, usage, precedent and a variety of statutes and legal instruments. An explicit understanding of such a constitution can be developed through commentary by the judiciary, government committees or legal experts. In such a constitutional system, all these elements may be recognized by courts, legislators, and the bureaucracy as binding upon government and limiting its powers. Such a framework is sometimes imprecisely called an "unwritten constitution"; however, all the elements of an uncodified constitution are typically written down in a variety of official documents, though not codified in a single document. However, there may be truly "unwritten" constitutional conventions which while not usually legally enforceable may hold just as much sway as the letter of the law.

The Commonwealth of Nations, often referred to as the British Commonwealth or simply the Commonwealth, is an international association of 56 member states, the vast majority of which are former territories of the British Empire from which it developed. They are connected through their use of the English language and cultural and historical ties. The chief institutions of the association are the Commonwealth Secretariat, which focuses on intergovernmental relations, and the Commonwealth Foundation, which focuses on non-governmental relations between member nations. Numerous organisations are associated with and operate within the Commonwealth.