The Free State of Thuringia (German: Freistaat Thüringen, pronounced [ˈfʁaɪʃtaːt ˈtyːʁɪŋən], English /θjʊərˈrɪndʒiə/) is a state of Germany, located in the central part of the country. It has an area of 16,171 square kilometres (6,244 sq mi) and 2.29 million inhabitants, making it the sixth smallest by area and the fifth smallest by population of Germany's sixteen states. Most of Thuringia is within the watershed of the Saale, a left tributary of the Elbe. Its capital is Erfurt.

Thuringia has been known by the nickname of "the green heart of Germany" (das grüne Herz Deutschlands) from the late 19th century, due to the dense forest that covers the terrain.

Thuringia is well known in Germany for nature and winter sports. It is home to the Rennsteig, Germany's most famous hiking trail, and the winter resort of Oberhof. Germany has won more Winter Olympics gold medals than any other country in the last 20 years, and half of Germany's gold medals have been won by Thuringian athletes.

From the northwest going clockwise, Thuringia borders on the German states of Lower Saxony, Saxony-Anhalt, Saxony, Bavaria and Hesse. The ridges of the western Harz Mountains divide the region from Lower Saxony on the north-west, while the eastern Harz similarly separates Thuringia from the state of Saxony-Anhalt to the north-east. To the south and southwest, the Thuringian Forest effectively separates the ancient region of Franconia, now the northern part of Bavaria, from the rolling plains of most of Thuringia. The central Harz range extends southwards along the western side into the northwest corner of the Thuringian Forest region, making Thuringia a lowland basin of rolling plains nearly surrounded by ancient somewhat-difficult mountains. To the west across the mountains and south is the drainage basin of the Rhine River.