Tambach-Dietharz is a town in the district of Gotha, in Thuringia, Germany. It is situated in the Thuringian Forest, 19 km south of Gotha.

Since 2012, Marco Schütz (independent) is the mayor. His predecessor was the former lieutenant from the German Army (Bundeswehr) Harald Wrona (FDP).

• The Falkenstein is a 96 m high, free standing porphyry rock. It is a natural monument and hiking destination. The mountain rescue hut at its foot is managed.
• The route from Schmalkalden to Tambach-Dietharz is signposted as Martin-Luther-Weg and is a walking route.
• In the autumn of 1989, a monument to the Swiss Theologian, and protagonist of the Bekennenden Kirche, Karl Barth was raised in front of the Haus Tannenberg. Barth gave his "Tambacher Rede" speech, that introduced a new positioning of protestant Christianity in the 20th century, in this house in 1919.

• Meister Eckhart (born about 1260; died before April 30, 1328), theologian, mystic and philosopher
• Karl-Heinz Menz (born 1949), biathlete
• Matthias Jacob (born 1960), biathlete
• Erich Recknagel (1904–1973), ski jumper, participant in the Olympic Winter Games in 1928
• Eisregen (formed 1995), death metal band, all original members came from Tambach-Dietharz