Greiz was once the capital of the smallest principality in Germany. Today, Greiz with its three castles is a unique historical cultural location. The impressive history of the Prussians contrasts with modern city life. The cityscape is characterized by the contrast of its natural location in the picturesque Elster Valley and the diverse architecture of Greiz. The first documented mention of the town dates back to 1209, with four castle men in "Groytz" named as witnesses in a deed of gift from the bailiff of Weida to the Mildenfurth monastery. While the village is documented as a "villa" in 1269, Greiz is first referred to as a town in 1359. In 1306, Greiz became the residence of the bailiffs and lords of Weida and Plauen and later of the Reussian lords.

In the following centuries, the Greiz area was repeatedly fragmented by frequent inheritance divisions. The highlight was the division of the town into Upper and Lower Greiz in 1564. The Reuß-Untergreiz line took up residence in the purpose-built Lower Castle, while the Obergreiz line resided in the Upper Castle. Both parts are reunited in 1768 when the Lower Greiz line dies out. The Greizer Reußen are elevated to the status of counts in 1763 and to hereditary imperial princes in 1778 and have their seat of power in Greiz until 1918. After the town fire of 1802, the House of Reuss Aelterer Linie took up residence in the Lower Castle, while the government of the principality was located in the Upper Castle. In 1920, the town became part of the state of Thuringia and in 1952, as a result of the territorial reform, it became a district town in the district of Gera. With the formation of today's Greiz district of Thuringia, the town of Greiz has been a district town since July 1, 1994.