Paris Convention for the Protection of Industrial Property
The Paris Convention for the Protection of Industrial Property, signed in Paris, France, on March 20, 1883, governs almost all international reciprocal patent filing rights. The Treaty is administered by the World Intellectual Property Organization (WIPO), based in Geneva, Switzerland.
The Paris Convention establishes a right of priority -- an applicant from one contracting state who files a patent application in a contracting state can use his or her first filing date as the effective filing date in another contracting state so long as the applicant files another application for the patent within a year from the first filing.
There are 169 countries who are contracting parties to the Paris Convention. You can view the list of contracting parties and obtain more information about the treaty at the World Intellectual Property Organization website: http://www.wipo.int/treaties/en/ip/paris/index.html.