Portugal is a founding member of NATO (1949), OECD and EFTA; it left the latter in 1986 to join the European Union. In 1996 it co-founded the Community of Portuguese Language Countries. It has a friendship alliance and dual citizenship treaty with Brazil. Portugal is part of the world's oldest active alliance through its treaty with the United Kingdom.

Portugal is a founding member of NATO (1949), OECD and EFTA; it left the latter in 1986 to join the European Union. In 1996 it co-founded the Community of Portuguese Language Countries. It has a friendship alliance and dual citizenship treaty with Brazil. Portugal is part of the world's oldest active alliance through its treaty with the United Kingdom.

The only international dispute concerns the municipality of Olivença. Under Portuguese sovereignty since 1297, the municipality of Olivença was ceded to Spain under the Treaty of Badajoz in 1801, after the War of the Oranges. Portugal claimed it back in 1815 under the Treaty of Vienna. Nevertheless, bilateral diplomatic relations between the two neighbouring countries are cordial, as well as within the European Union.