How many countries signed the Outer Space Treaty?

The Outer Space Treaty, formally the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, is a treaty that forms the basis of international space law. The treaty was opened for signature in the United States, the United Kingdom, and the Soviet Union on 27 January 1967, and entered into force on 10 October 1967. As of June 2019, 109 countries are parties to the treaty, while another 23 have signed the treaty but have not completed ratification. In addition, Taiwan, which is currently recognized by 14 UN member states, ratified the treaty prior to the United Nations General Assembly's vote to transfer China's seat to the People's Republic of China (PRC) in 1971.

Among the Outer Space Treaty's main points are that it prohibits the placing of nuclear weapons in space, it limits the use of the Moon and all other celestial bodies to peaceful purposes only, and establishes that space shall be free for exploration and use by all nations, but that no nation may claim sovereignty of outer space or any celestial body. The Outer Space Treaty does not ban military activities within space, military space forces, or the weaponization of space, with the exception of the placement of weapons of mass destruction in space. It is mostly a non-armament treaty and offers insufficient and ambiguous regulations to newer space activities such as lunar and asteroid mining.