This review explores the dual role of reactive oxygen species (ROS) and free radicals in the pathogenesis of endometriosis, aiming to deepen our understanding of these processes through a systematic literature review. To assess the induction and involvement of ROS in endometriosis, we conducted a comprehensive literature review using Cochrane Libraries, EMBASE, Google Scholar, PubMed, and SCOPUS databases. Of 30 qualifying papers ultimately reviewed, 28 reported a significant contribution of ROS to the pathogenesis of endometriosis, while two found no association. The presence of ROS in endometriosis is associated with infertility, irregular menstrual cycles, painful menstruation, and chronic pelvic discomfort. Among individual ROS types studied, hydrogen peroxide was most frequently investigated, followed by lipid peroxides and superoxide radicals. Notable polymorphisms associated with ROS in endometriosis include those for AT-rich interactive domain 1A (ARID1A) and quinone oxidoreductase 1 (NQO1) isoforms. Key enzymes for ROS scavenging and detoxification include superoxide dismutase, glutathione, and glutathione peroxidase. Effective inhibitors of ROS related to endometriosis are vitamins C and E, astaxanthin, fatty acid-binding protein 4, cerium oxide nanoparticles (nanoceria), osteopontin, sphingosine 1-phosphate, N-acetyl-L-cysteine, catalase, and a high-antioxidant diet. Elevated levels of ROS and free radicals are involved in the pathogenesis of endometriosis, suggesting that targeting these molecules could offer potential therapeutic strategies.