BackgroundDifficulties in deploying mental health assessments during disasters have resulted in emerging research examining the use of social media as a population mental health monitoring tool. This review synthesises this literature, with particular focus on research methods and applications.MethodsThe field of social media monitoring of mental health during disasters was rapidly mapped using a scoping review methodology. Six interdisciplinary research databases were searched for relevant articles, with data extracted on the articles’ applications and data collection and analysis methods. Articles were then synthesised via narrative review.ResultsForty-seven papers were identified. Three application themes emerged, including: (i) estimating mental health burden; (ii) planning or evaluating interventions and policies, and (iii) knowledge discovery, where theories of human behaviour and mental health were evaluated. Applications across 30 mental health issues were identified, with mental health typically assessed using established linguistic dictionaries. Features extracted from social media data included linguistic, psycholinguistic, behavioural, and demographic features. Analytic techniques involved machine learning, statistical modelling, and qualitative analyses.ConclusionsThe application of social media monitoring has considerable potential for measuring the mental health impact on populations during disasters. As an emerging field, opportunities for further work were identified to improve mental health assessment methods, examine specific mental health conditions, and trial tools in real-world settings. Platforms integrated with such techniques may offer significant benefits for monitoring mental health in contexts where formal assessments are difficult to deploy, and may potentially be harnessed to monitor the impact of response efforts and intervention delivery.