國家承認開始成爲國際法的問題，始於十八世紀末葉美國獨立時，法國對美國給予國家承認，結果引起英國的不滿甚至爲此對法國宣戰。十九世紀時，由於中南美各國紛紛獨立，再度引起殖民母國與其他國家在國家承認問題上的爭議，從而促使國家承認制度正式成爲國際法體系的一部分。國家承認是個別國家的權利，但在國際社會的實際運作中，對於承認新國家的問題，有時是在國際會議中共同討論達成合意之後，再透過條約承認某國獨立，或集體於同一時期給予承認，希望能產生促使他國跟進的效果，以形成新國家被承認的穩定狀態，此即是一般所謂的集體承認。歐盟自成立以來曾針對波羅的海國家、巴爾幹半島的前南斯拉夫聯邦各國、蘇聯解體後新成立的各國、巴勒斯坦的承認做成決議，甚至歐盟對西班牙新近通過獨立公投的加泰隆尼亞獨立亦發表看法，這些事例在國際法上有何意義？這些歐盟的國家承認實踐是本文探討的主體。

In the late 18th century, the state recognition of the United State lead to the war between the French and the United Kingdom. Since then, the state recognitions become an important issue in the international law. In the 19th century, the dispute of the independence of the Central and South American countries make the state recognitions become one part of the system of the international law. The state recognition is the right of a country. However, most of the decisions of the state recognitions decided by an international meeting, international agreement, or collective recognition, aim at the impersonation of other countries. In the past, the European Union has made the state recognition to the countries of the Baltic Sea, the former Yugoslavia in the Balkans, the newly established states after the Soviet Union's dissolution, and the Palestine. The European Union has also comment on the independence of Catalonia. Therefore, what is the meaning of these examples in international law? These European Union's state recognitions are main topics of this research.