Didorong oleh pesatnya urbanisasi, peningkatan kesadaran akan kesehatan, dan perubahan preferensi konsumen, industri air minum dalam kemasan (AMDK) Indonesia telah mengalami pertumbuhan yang pesat. Dalam perkembangan ini, AMDK X muncul sebagai pesaing utama yang berhasil menantang dominasi Aqua yang telah lama mendominasi pasar. Penelitian ini bertujuan untuk mengkaji pengaruh Social Media Marketing Activities (SMMA) terhadap Brand Loyalty, melalui Brand Awareness dan Brand Image. Elemen-elemen kunci SMMA yang dianalisis meliputi Entertainment, Interactivity, Trendiness, Electronic Word-of- Mouth (e-WOM), dan Informativeness. Penelitian ini menggunakan pendekatan kuantitatif, dengan data yang dikumpulkan dari 200 responden, yaitu konsumen AMDK X di Medan, yang kemudian dianalisis menggunakan SPSS. Hasil penelitian menunjukkan bahwa Interactivity, Trendiness, dan e-WOM secara signifikan meningkatkan Brand Awareness, sementara Interactivity, Trendiness, e- WOM, dan Informativeness memberikan dampak positif terhadap Brand Image. Brand Awareness dan Brand Image, pada gilirannya, terbukti berperan penting dalam mendorong Brand Loyalty. Namun, Entertainment tidak menunjukkan pengaruh langsung terhadap Brand Image, dan Informativeness tidak memengaruhi Brand Awareness. / Driven by rapid urbanization, increased health awareness, and shifting consumer preferences, the Indonesian bottled water industry (AMDK) has experienced significant growth. Amid this development, AMDK X has emerged as a key competitor, successfully challenging Aqua's long-standing dominance in the market. This study aims to examine the impact of Social Media Marketing Activities (SMMA) on Brand Loyalty, mediated by Brand Awareness and Brand Image. The key SMMA elements analyzed include Entertainment, Interactivity, Trendiness, Electronic Word-of-Mouth (e-WOM), and Informativeness. Using a quantitative approach, data was collected from 200 respondents, AMDK X consumers in Medan, and analyzed using SPSS. The results show that Interactivity, Trendiness, and e-WOM significantly enhance Brand Awareness, while Interactivity, Trendiness, e-WOM, and Informativeness positively influence Brand Image. Both Brand Awareness and Brand Image play a significant role in driving Brand Loyalty. However, Entertainment does not have a direct impact on Brand Image, and Informativeness does not affect Brand Awareness.