The Tiras Mountains are a mountain range and private nature reserve in southern Namibia, about 20 kilometres west of Helmeringhausen.
The Tiras Mountains are the intersection of four different landscapes: from the north and north-east, the Tiras Mountains merge with the mountainous landscape of the Rooirand (Rotrand) and the adjoining Tsaris Mountains to the north; from the west and south-west, the red dunes of the Neisib Plateau and Homs Plateau form the contact with the Namib-Naukluft National Park and the foothills of the Namib Desert.
Towards the south-east, the Tiras Mountains border on a savannah and succulent steppe, which also has ancient rock paintings of bushmen (San). In the adjoining short shrub savannah, cattle breeding is practised, especially with cattle.
Important peaks of the Tiras Mountains are Schanzenberg (1902 m), Sattelberg (1419 m), Koiimasis Nase (1397 m) and Bergveld.
The 125,000 ha (125 km²) private nature reserve has existed since March 1998. It consists of eight (as of September 2018) farms used for tourism and extensive agriculture (Gunsbewys, Tiras, Koiimasis, Landsberg, Numis, Weissenborn, Korais, Excelsior).