BACKGROUND: The increasing trend in unnecessary caesarean sections has caused maternal and neonatal health concerns worldwide. Various medical and non-medical interventions have been designed and implemented to reduce caesarian section overuse. However, their efficacy is questionable. AIMS: This study aimed to identify and classify effective interventions to reduce unnecessary caesarian sections. METHODS: We searched EMBASE, MEDLINE, Web of Knowledge and Scopus databases for articles, using appropriate search strategies, up to 2 June 2020. Overall, 7951 identified articles were screened and assessed using a valid quality assessment checklist. Finally, 109 eligible studies were included in this review. Thematic content analysis was used to identify and classify the effective interventions. RESULTS: Overall, 188 effective caesarian section reduction measures were identified. They were categorized into 45 actions, 16 intervention groups and 6 WHO building blocks, including "governance and leadership", "financing", "health workforce", "medical products and technologies", "information" and "service delivery". Using qualified and competent staff, intra-partum services, and oversight were the most commonly applied interventions to reduce unnecessary caesarian sections. CONCLUSIONS: A taxonomy of effective strategies to reduce unnecessary caesarian sections was developed in this study. A holistic approach is crucial to addressing the new epidemic of unnecessary caesarian section. Multiple interventions based on the underlying causes of caesarian section overuse should be designed and implemented at local and global levels.