The prehistory of Southeast Europe, defined roughly as the territory of the wider Southeast Europe (including the territories of the modern countries of Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Greece, Kosovo, Moldova, Montenegro, North Macedonia, Romania, Serbia, Slovenia, and European Turkey) covers the period from the Upper Paleolithic, beginning with the presence of Homo sapiens in the area some 44,000 years ago, until the appearance of the first written records in Classical Antiquity, in Greece. First Greek language is Linear A and follows Linear B, which is a syllabic script that was used for writing in Mycenaean Greek, the earliest attested form of the Greek language. The script predates the Greek alphabet by several centuries. The oldest Mycenaean writing dates to about 1400 BC. It is descended from the older Linear A, an undeciphered earlier script used for writing the Minoan language, as is the later Cypriot syllabary, which also recorded Greek. Linear B, found mainly in the palace archives at Knossos, Kydonia, Pylos, Thebes and Mycenae, but disappeared with the fall of the Mycenean civilisation during the Late Bronze Age collapse.

Human prehistory in Southeast Europe is conventionally divided into smaller periods, such as Upper Paleolithic, Holocene Mesolithic/Epipaleolithic, Neolithic Revolution, expansion of Proto-Indo-Europeans, and Protohistory. The changes between these are gradual. For example, depending on interpretation, protohistory might or might not include Bronze Age Greece (3000–1200 BC), Minoan, Mycenaean, Thracian and Venetic cultures. By one interpretation of the historiography criterion, Southeast Europe enters protohistory only with Homer (See also Historicity of the Iliad, and Geography of the Odyssey). At any rate, the period ends before Herodotus in the 5th century BC.

The earliest evidence of human occupation discovered in the region, in Kozarnika cave (Bulgaria), date from at least 1.5 million years ago.

There is evidence of human presence in the Southeastern Europe from the Lower Paleolithic onwards, but the number of sites is limited. According to Douglass W. Bailey:

it is important to recognize that the Southeastern Europe Upper Palaeolithic was a long period containing little significant internal change. Thus, regional transition was not as dramatic as in other European regions. Crucial changes that define the earliest emergence of Homo sapiens sapiens are presented at Bacho Kiro at 44,000 BC. The Bulgarian key Palaeolithic caves named Bacho Kiro and Temnata Dupka with early Upper Palaeolithic material correlate that the transition was gradual.

The Palaeolithic period, literally the “Old Stone Age”, is an ancient cultural level of human development characterized by the use of unpolished chipped stone tools. The transition from Middle to Upper Palaeolithic is directly related to the development of behavioural modernity by hominids around 40,000 years BP. To denote the great significance and degree of change, this dramatic shift from Middle to Upper Palaeolithic is sometimes called the Upper Palaeolithic Revolution.

In the late Pleistocene, various components of the transition–material culture and environmental features (climate, flora, and fauna) indicate continual change, differing from contemporary points in other parts of Europe. The aforementioned aspects leave some doubt that the term Upper Palaeolithic Revolution is appropriate to the Balkans.

In general, continual evolutionary changes are the first crucial characteristic of the transition to the Upper Palaeolithic in the region. The notion of the Upper Palaeolithic Revolution that has been developed for core European regions is not applicable to the region. What is the reason? This particularly significant moment and its origins are defined and enlightened by other characteristics of the transition to upper Old Stone Age. The environment, climate, flora and fauna corroborate the implications.