Female College Students are a interesting market for the cosmetic industry in marketing their products. This study aims to identify the effect of social media marketing activity on the purchase intention of cosmetic through brand loyalty. The respondents of this study were female university students in Makassar City, South Sulawesi Province, Indonesia, who were followers of cosmetic brand social media accounts. The research hypothesis was analysed using Structural Equation Modelling using SPSS_AMOS 23 program. The results based on 288 samples showed that social media marketing directly had a significant effect on cosmetic brand loyalty, brand loyalty directly had a significant impact on purchase intentions of cosmetic products, marketing through Social media does not have a substantial effect on the purchase intention of cosmetic products, marketing through social media has a significant impact on the purchase intention of cosmetic products through brand loyalty. These results indicate that although marketing through social media does not substantially impact female college students' purchase intentions, this effect will be significantly mediated by loyalty to cosmetic brands. Therefore, brand loyalty needs to be appropriately managed to increase the purchase intention of cosmetic products among female college students in Makassar City, Indonesia.