This thesis analyzes modern Greek enlightenment and 19th century Greek Nationalism, in the light of nationalism theories. It confronts with the process of Modern Greek enlightenment which took place within the lands of the Ottoman Empire and the Greek nationalism which was the second phase of the modern Greek enlightenment. The thesis argues that the lands where today Greeks live had been invaded and settled by various ethnic groups. As a result it lost its ethnic ties with the ancient Greeks. Modern Greeks are not the descendants of ancient Greeks as they accept. Modern Greek national identity is a constructed one and Greek nation which is a mixture of different Balkan Orthodox people such as Slavs, Albanians, Macedonians and Bulgars. Greek Nation was built within the Ottoman Millet system by the help of the European Philhellenes and Greek intellectuals. This assumption is based on Fallmayer theory which suggests that ancient Greeks had disappeared completely and the modern Greeks were merely descendants of Slavs and Albanians.