European Union enlargement: The EU announces that Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia will become members on May 1, 2004.

The largest enlargement of the European Union (EU), in terms of number of states and population, took place on 1 May 2004.

Cyprus, officially the Republic of Cyprus, is an island country in the eastern Mediterranean Sea. Situated in West Asia, its cultural identity and geopolitical orientation are overwhelmingly Southeast European. Cyprus is the third largest and third most populous island in the Mediterranean, after Sicily and Sardinia. It is located southeast of Greece, south of Turkey, west of Syria and Lebanon, northwest of Palestine and Israel, and north of Egypt. Its capital and largest city is Nicosia. Cyprus hosts the British military bases Akrotiri and Dhekelia, whilst the northeast portion of the island is de facto governed by the self-declared Turkish Republic of Northern Cyprus, which is separated from the Republic of Cyprus by the United Nations Buffer Zone.

The Czech Republic, also known as Czechia and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The Czech Republic has a hilly landscape that covers an area of 78,871 square kilometers (30,452 sq mi) with a mostly temperate continental and oceanic climate. The capital and largest city is Prague; other major cities and urban areas include Brno, Ostrava, Plzeň and Liberec.

Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Russia. The territory of Estonia consists of the mainland, the larger islands of Saaremaa and Hiiumaa, and over 2,300 other islands and islets on the east coast of the Baltic Sea. Its capital Tallinn and Tartu are the two largest urban areas. The Estonian language is the official language and the first language of the majority of its population of nearly 1.4 million. Estonia is one of the least populous members of the European Union and NATO.