This systematic literature review (SLR) aims to synthesize eight empirical studies (2018-2026) regarding social media fatigue (SMF) and digital fatigue in the context of social media marketing, including the works of Bright and Logan (2018), Milas and Lesinger (2022), Fernandes and Oliveira (2024), Qin et al. (2024), Zhang et al. (2020), Baj-Rogowska (2023), Fitriani (2025), and the Gen Z study (2026). The synthesis results show that SMF is triggered by external factors (excessive branded content, intrusive advertising, influencer information pressure) and internal factors (FOMO, privacy concerns, compulsive use), which encourage lurking, avoidance, social anxiety, and decreased purchase intention and engagement. These findings have implications for digital marketers, platform managers, and social media marketing researchers.