The Sierra de Lema is an upland mountain range area with tepuis, located in Bolívar state of southeastern Venezuela.

[2] It is partly within the bounds of Canaima National Park[3] and encompasses a number of prominent tepuis, including the entire Los Testigos chain and Ptari Massif.

[2] Because the toponymy of the region remains largely unresolved, the stated length of the Sierra de Lema can vary widely, depending on the definition used.

[5] The El Mirador ("The Lookout") area at the base of the Sierra de Lema exhibits unusually high levels of the radioisotope Caesium-137, in both its soils and vegetation.

[4][8] The Sierra de Lema consists of an igneous-metamorphic basement overlain by Precambrian sedimentary rocks of the Roraima Group, with Mesozoic diabase intrusions.