The current investigation was pointed at developing and progressively validating novel, simple, responsive and stable RP-HPLC method for the measurement of active pharmaceutical ingredients of Ritonavir and Nirmatrelvir and their related substances. A simple, selective, validated and well-defined stability that shows gradient RP-HPLC methodology for the quantitative determination of ritonavir and nirmatrelvir. The chromatographic strategy utilized Column of Dikma Spursil C18 (4.6 x 150mm, 3m), using isocratic elution with a mobile phase of 0.1 percent Formic acid and Acetonitrile (65:35). A flow rate of 1 ml/min and a detector wavelength of 253 nm utilizing the PDA detector were given in the instrumental settings. Using the impurity-spiked solution, the chromatographic approach was streamlined. Validation of the proposed method was carried out according to an international conference on harmonization (ICH) guidelines. LOD and LOQ for the two active ingredients and their impurities were established with respect to test concentration. The calibration charts plotted were linear with a regression coefficient of R2=0.999, which means the linearity was within the limit. Recovery, specificity, linearity, accuracy, robustness, ruggedness was determined as a part of method validation and the results were found to be within the acceptable range. The proposed method to be fast, simple, feasible and affordable in RS condition. During stability tests, it can be used for routine analysis of production samples and to verify the quality of drug samples during stability studies.