The Turnhalle (English: gymnasium) is a building in Windhoek, the capital of Namibia. Built during the era of Imperial Germany's colonisation of South-West Africa, it has been through a variety of uses, most prominently as the venue for the 1975–1977 Turnhalle Constitutional Conference, an attempt to quell armed resistance waged by the People's Liberation Army of Namibia against South African occupation. The Turnhalle housed the Tribunal court of the Southern African Development Community (SADC) until disbandment in 2012.
Soon after the foundation of modern Windhoek in October 1890, a posh suburb developed on the slope of the hill opposite the city's railway station. The first Turners club, a German gymnastics association influenced by the suggestions of Turnvater Jahn, was founded in 1899. Exercise and practice took place where the Turnhalle stands today. A temporary corrugated iron structure was erected in 1905.
On 6 March 1909, the foundation for a 22 m x 14 m gymnasium with high ceilings and a street-facing gable was laid. The Turnhalle building was inaugurated nine months later on 11 December 1909. The neo-classicist building of Wilhelmine architecture was regarded as "the most beautiful building in the northern part of town", and it was the first timber-girdered roof structure in the German colony.
Soon the building grew too small for its purpose. A double-storey extension was appended on the western side of the building during the years of 1912 and 1913. The date inscription above the main entrance refers to this extension. Architect Otto Busch designed both parts of the building. Master architect Wilhelm Sander's proposal was ignored for the extension.
The Turnhalle was used for school physical training and gymnastic competitions, as well as for recreational sports. During World War I it accommodated South African troops. After a stage was added, the building was also used for theatre performances and cinema. After Namibian independence in 1990, the Turnhalle was used as conference venue, and for the National Council of Namibia, until that body moved to Tintenpalast. Afterwards it was earmarked to accommodate the SADC Tribunal court but burned down on 18 January 2007. It has been restored since then; the SADC Tribunal became operational in April of the same year.