Is Eritrea the newest country of the world?

No. It is one of the world's newest countries, since it did not get its Independence from Ethiopia until 1993, but Eritrea is not the newest country. There are 3 more countries that are newer than Eritrea. East Timor claimed its Independence from Indonesia in 2002. Kosovo claimed its Independence from Serbia in 2010. South Sudan is the world's newest country, since it did not get its Independence from Sudan until 2012.