Index on Censorship is an organisation campaigning for freedom of expression, which produces a quarterly magazine of the same name from London. It is directed by the non-profit-making Writers and Scholars International, Ltd (WSI) in association with the UK-registered charity Index on Censorship, which are both chaired by the British television broadcaster, writer and former politician Trevor Phillips. Index is based at 1 Rivington Place in central London.

Freedom of speech is a principle that supports the freedom of an individual or a community to articulate their opinions and ideas without fear of retaliation, censorship, or legal sanction. The right to freedom of expression has been recognised as a human right in the Universal Declaration of Human Rights and international human rights law by the United Nations. Many countries have constitutional law that protects free speech. Terms like free speech, freedom of speech, and freedom of expression are used interchangeably in political discourse. However, in a legal sense, the freedom of expression includes any activity of seeking, receiving, and imparting information or ideas, regardless of the medium used.