Which country was the last to join the European Union as its 28th member?

Croatia is recognized as the 28th and most recent member to join the European Union, officially becoming a member on July 1, 2013. This addition marked an important milestone for both Croatia and the EU, as it represented Croatia's commitment to democratic reforms and economic development after gaining independence from Yugoslavia in the early 1990s.

Other countries listed, such as Greece, Poland, and Spain, joined the European Union earlier. Greece became a member in 1981, Spain in 1986, and Poland joined the EU much later in 2004. Thus, Croatia's accession in 2013 is the most recent, solidifying its position as the last country to join the EU at that time.