Cancer is a leading cause of death worldwide, affecting millions of people across all demographics. The development of cancer is a multifactorial process influenced by genetic, environmental, and lifestyle factors. This article explores the main causes of cancer, delving into genetic mutations, carcinogens, lifestyle choices such as diet, smoking, and physical activity, and environmental exposures like radiation and pollutants. It aims to provide an in-depth understanding of how these factors interplay in the onset of cancer, as well as potential preventive measures. By recognizing the primary causes of cancer, we can work toward better prevention, earlier detection, and improved treatment outcomes.