The Vienna Convention on the Law of Treaties (VCLT) is a treaty concerning the international law on treaties between states. It was adopted on 22 May 1969 and opened for signature on 23 May 1969. The Convention entered into force on 27 January 1980.
As of January 2018, 116 state parties have ratified the convention, and a further 15 states have signed but have not ratified the convention. In addition, the Republic of China (Taiwan), which is currently only recognized by , signed the Convention in 1970 prior to the United Nations General Assembly's vote to transfer China's seat to the People's Republic of China (PRC) in 1971. When the PRC subsequently acceded to the Convention, they described the Republic of China's (ROC) signature as "illegal". 64 UN member states have neither signed nor ratified the Convention.
List of parties
List of signatories that have not ratified
Partially recognized state
The Republic of China (Taiwan), which is currently only recognized by , signed 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. When the PRC subsequently acceded the treaty, they described the Republic of China's (ROC) signature as "illegal".