Reactive oxygen species (ROS) play a dual role in cancer, influencing both tumor growth and regression. Their intricate involvement in cellular processes underscores the necessity of maintaining a delicate ROS balance for normal cellular function. Intriguingly, while ROS contribute to tumor progression, they also exhibit the potential to selectively kill cancer cells. Emerging therapeutic strategies focus on modulating ROS levels within cancer cells, considering the type of radicals generated, their site of formation, and concentration gradients. This review delves into recent advancements in understanding the impact of ROS on the tumor microenvironment and cancer treatment. By exploring the interplay between ROS dynamics and therapeutic outcomes, this study provides a comprehensive perspective on the pivotal role of oxygen‐related free radicals in cancer therapy and highlights the innovative approaches and insights shaping this rapidly evolving field.