This study aims to search for the effect of the Demarketing strategy with its dimensions (price raising, counter-advertising, distribution, reducing product quality), on the brand reputation in its dimensions (brand reliability, brand charity), in bodybuilding centers in Al-Diwaniyah Governorate, and a problem was presented The study in a main question (what is the effect of the Demarketing strategy on the reputation of the brand), and the study sample included the users of nutritional supplements in the centers, and the questionnaire was used in collecting data, as 386 responses were obtained from users of nutritional supplements in the bodybuilding centers In Al-Qadisiyah Governorate, using the random sampling method in Al-Diwaniyah Governorate, and the descriptive analytical approach was adopted in the study, and then the data was analyzed by adopting some statistical methods such as (arithmetic mean, standard deviation, linear correlation coefficient, simple and multiple regression coefficient) and to test the scale was employed (Alpha Cronbach, factor analysis), and the results were reached using the statistical program such as (SPSS.V.27) and the program (Amos.V.26), as the results of the study confirmed That there is an impact of a Demarketing strategy on a brand's reputation.