The present method provides the detailed description of development and validation of a simple stability indicating reverse phase column liquid chromatographic method for Olmesartan in the presence of its impurities namely Imp-A, Imp-B, Imp-C, Imp-D, Imp-E, Imp-F and Imp-G and degradation products generated from forced degradation studies. The drug substance was subjected to stress conditions of aqueous hydrolysis, Oxidative, photolytic and thermal stress degradation. The degradation of Olmesartan was observed under acid hydrolysis, base hydrolysis and peroxide. The drug was found to be stable to other stress conditions attempted. Successful separation of the drug from synthetic impurities and degradation products formed under stress conditions was achieved on symmetry C18, 150 mm × 4.6 mm, 5 μ column using a phosphate buffer, Acetonitrile and Milli Q water. The developed LC method was validated with respect to specificity, linearity, accuracy, precision, raggedness and robustness. The assay method was found to be linear in the range of 250 μg·mL -1 to with 1000 μg·mL -1 correlation coefficient of 0.9999 and the linearity of the impurities was established from LOQ to 0.4%. Recoveries of assay and impurities were found between 98.5% and 101.2%. The developed LC method to determine the related substances and assay determinations of Olmesartan can be used to evaluate the quality of regular production samples and stability samples. To best of our knowledge, the validated stability indicating LC method which separates all the impurities disclosed in this investigation was not published elsewhere.