Dianabol (methandrostenolone) is a potent oral androgen and anabolic steroid (AAS) used primarily to enhance physical performance and build muscle mass. It acts as an androgen receptor agonist, promoting significant protein synthesis and nitrogen retention. However, it is largely no longer prescribed medically, is illegal for non-medical use in many countries (Schedule III in the US), and carries high risks of side effects, including liver toxicity.