The Paris Convention for the Protection of Industrial Property is an international agreement relating to intellectual property that first went into force in 1883. Its trademark-related provisions provide that foreign nationals’ rights get the same treatment as domestic individuals and companies, that trademarks filed in one signatory country can be filed for in another jurisdiction that has acceded to the Convention and get the benefit of the filing date in the first country, that registration of a mark in the applicant’s “home” jurisdiction must be an acceptable basis for registration in other member countries, and that collective marks must be recognized.
Applications filed in the United States Patent & Trademark Office can claim priority under the Paris Convention (or due to other, generally bilateral treaties) under Section 44(d) of the Lanham Act, the U.S. federal trademark law, while Section 44(e) provides a registration basis in the U.S. where the mark is registered in the applicant’s “home” jurisdiction. U.S. applications where the applicant has a pending application in its “home” jurisdiction that is not registered yet also use Section 44(d) as a filing basis.
You can view a list of current members on the World Intellectual Property Organization’s website here.