(17α)-(±)-13-Ethyl-3-methoxy-18,19-dinorpregna-2,5(10)-dien-20-yn-17-ol, commonly known as Levonorgestrel Impurity T, is a structurally defined organic compound. It is a stereoisomer and a key process-related impurity of Levonorgestrel, a widely used synthetic progestogen. Its chemical structure is closely related to the active pharmaceutical ingredient, differing in the configuration at the C17 position. This compound is primarily used as a certified reference material (CRM) or impurity standard in the pharmaceutical industry. Its main application is in the analytical quality control of Levonorgestrel drug substances and finished products. It is essential for method development, validation, and routine testing to monitor and control impurity levels, ensuring the safety, efficacy, and compliance of hormonal contraceptives and other therapeutic formulations containing Levonorgestrel with stringent pharmacopeial standards (e.g., USP, EP). As a high-purity analytical standard, it is critical for conducting stability studies, assessing manufacturing process consistency, and fulfilling regulatory submission requirements for drug approval and post-marketing surveillance. Proper handling requires adherence to laboratory safety protocols for chemical substances.