In biogeography, the Mediterranean basin (/ˌmɛdɪtəˈreɪniən/ MED-ih-tə-RAY-nee-ən), also known as the Mediterranean region or sometimes Mediterranea, is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and warm to hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation.

The Mediterranean basin covers portions of three continents: Africa, Asia, and Europe. It is not the same as the drainage basin of the Mediterranean Sea; the drainage basin is larger, as rivers including the Nile and Rhône reach further into Africa and Europe. Conversely, the Mediterranean basin includes regions not in the drainage basin, such as Iraq, Jordan, and Portugal.

It has a varied and contrasting topography. The Mediterranean region offers a varied landscape of high mountains, rocky shores, impenetrable scrub, semi-arid steppes, coastal wetlands, sandy beaches and a myriad of islands of various shapes and sizes dotted amidst the clear blue sea. Contrary to the classic sandy beach images portrayed in most tourist brochures, the Mediterranean is surprisingly hilly. Mountains can be seen from almost anywhere.

By definition, the Mediterranean basin extends from Macaronesia in the west, to the Levant in the east, although some places may or may not be included depending on the view, as is the case with Macaronesia: some definitions only include the Canary Islands and Madeira while others include the whole Macaronesia (with the Azores and Cape Verde).

The northern portion of the Maghreb region of north-western Africa has a Mediterranean climate, separated from the Sahara Desert, which extends across North Africa, by the Atlas Mountains. In the eastern Mediterranean the Sahara extends to the southern shore of the Mediterranean, with the exception of the northern fringe of the peninsula of Cyrenaica in Libya, which has a dry Mediterranean climate.

In West Asia, it covers the western and southern portions of the Anatolian Peninsula, as far as Iraq, but excluding the temperate-climate mountains of central Turkey. It includes the Mediterranean Levant at the eastern end of the Mediterranean, bounded on the east and south by the Negev and Syrian deserts.

Europe lies to the north of the Mediterranean. The European portion of the Mediterranean basin loosely corresponds to Southern Europe. The three large Southern European peninsulas, the Apennine Peninsula, the Balkan Peninsula, and the Iberian Peninsula, extend into and comprise much of the Mediterranean-climate zone. A system of folded mountains, including the Pyrenees dividing Spain from France, the Alps dividing Italy from Central Europe, the Dinaric Alps along the eastern Adriatic, and the Balkan and Rila-Rhodope mountains of the Balkan Peninsula divide the Mediterranean from the temperate climate regions of Central Europe, Eastern Europe, and Northern, North-western, or Western Europe.

The Mediterranean basin was shaped by the ancient collision of the northward-moving African–Arabian continent with the stable Eurasian continent. As Africa–Arabia moved north, it closed the former Tethys Sea, which formerly separated Eurasia from the ancient super continent of Gondwana, of which Africa was part. At about the same time, 170 mya in the Jurassic period, a small Neotethys ocean basin formed shortly before the Tethys Sea was closed at the eastern end. The collision pushed up a vast system of mountains, extending from the Pyrenees in Spain to the Zagros Mountains in Iran. This episode of mountain building, known as the Alpine orogeny, occurred mostly during the Oligocene (34 to 23 million years ago (mya)) and Miocene (23 to 5.3 mya) epochs. The Neotethys became larger during these collisions and associated folding and subduction.