Mitochondrial metabolism and reactive oxygen species (ROS) generation are essential for Kras-mediated tumorigenicity. This study shows that glucose metabolism supports the pentose phosphate pathway, which is crucial for Kras-induced anchorage-independent growth. Glycolytic ATP is necessary for growth under hypoxic conditions. Glutamine metabolism through the tricarboxylic acid (TCA) cycle, specifically via glutaminase and alanine aminotransferase, is essential for Kras-induced growth. Mitochondrial metabolism generates ROS, which regulate the ERK MAPK signaling pathway, promoting Kras-induced growth. The Q₀ site of mitochondrial complex III is the major source of ROS required for anchorage-independent growth. Loss of the mitochondrial transcription factor A (TFAM) gene reduces tumorigenesis in a Kras-driven lung cancer model. These findings demonstrate that mitochondrial metabolism and ROS generation are essential for Kras-induced cell proliferation and tumorigenesis. The Warburg effect, characterized by aerobic glycolysis in tumor cells, is a key feature of cancer metabolism. While the role of mitochondria in tumor cells has been debated, this study highlights their critical function in supporting Kras-driven tumorigenesis. Mitochondrial metabolism provides substrates for the pentose phosphate pathway, generates ATP, and produces ROS, which are essential for tumor cell survival and proliferation. The study also shows that glutamine catabolism by the TCA cycle is crucial for tumor growth, even in the absence of glucose. Mitochondrial ROS, particularly from complex III, are required for cell proliferation and anchorage-independent growth. The results indicate that mitochondrial function is essential for tumorigenesis, as evidenced by the reduced tumorigenicity in mice with impaired mitochondrial function. Overall, the study underscores the importance of mitochondrial metabolism and ROS generation in Kras-mediated tumorigenesis.Mitochondrial metabolism and reactive oxygen species (ROS) generation are essential for Kras-mediated tumorigenicity. This study shows that glucose metabolism supports the pentose phosphate pathway, which is crucial for Kras-induced anchorage-independent growth. Glycolytic ATP is necessary for growth under hypoxic conditions. Glutamine metabolism through the tricarboxylic acid (TCA) cycle, specifically via glutaminase and alanine aminotransferase, is essential for Kras-induced growth. Mitochondrial metabolism generates ROS, which regulate the ERK MAPK signaling pathway, promoting Kras-induced growth. The Q₀ site of mitochondrial complex III is the major source of ROS required for anchorage-independent growth. Loss of the mitochondrial transcription factor A (TFAM) gene reduces tumorigenesis in a Kras-driven lung cancer model. These findings demonstrate that mitochondrial metabolism and ROS generation are essential for Kras-induced cell proliferation and tumorigenesis. The Warburg effect, characterized by aerobic glycolysis in tumor cells, is a key feature of cancer metabolism. While the role of mitochondria in tumor cells has been debated, this study highlights their critical function in supporting Kras-driven tumorigenesis. Mitochondrial metabolism provides substrates for the pentose phosphate pathway, generates ATP, and produces ROS, which are essential for tumor cell survival and proliferation. The study also shows that glutamine catabolism by the TCA cycle is crucial for tumor growth, even in the absence of glucose. Mitochondrial ROS, particularly from complex III, are required for cell proliferation and anchorage-independent growth. The results indicate that mitochondrial function is essential for tumorigenesis, as evidenced by the reduced tumorigenicity in mice with impaired mitochondrial function. Overall, the study underscores the importance of mitochondrial metabolism and ROS generation in Kras-mediated tumorigenesis.