Background: Lenacapavir is a selective inhibitor of HIV-1 capsid protein and has demonstrated potent anti-viral activity used for the treatment of multidrug-resistant Human Immunodeficiency Virus type 1 (HIV-1) infection. Method: A new, simple, accurate, rapid, precise, reproducible and cost-effective RP-HPLC method for the quantitative estimation of Lenacapavir in bulk and pharmaceutical dosage form. The developed RP-HPLC method for the quantitative estimation of Lenacapavir is based on measurement of absorption at maximum wavelength 240 nm using 2% Sodium Benzoate and Methanol (50:50% v/v) as a solvent. The stock solution of Lenacapavir was prepared, and subsequent suitable dilution was prepared in mobile phase to obtained standard curve. The standard solution of Lenacapavir shows absorption maxima at 240 nm. Results: The Lenacapavir obeyed Beer Lambert’s law in the concentration range of 20-100μg/ml with regression 0.999 at 240 nm. The overall % recovery was found to be 99.78% for Lenacapavir which reflects that the method was free from the interference of the impurities and other excipients, used in the bulk and marketed dosage form. The low value of % RSD was indicative of accuracy and reproducibility of the method. The % RSD for inter-day and intra-day precision was found to be 0.2 for Lenacapavir respectively which is <2% hence proved that method is precise.