IntroductionCaesarean section (CS) rates are increasing globally. CS can be a live-saving procedure when medically indicated, but it comes with higher risks for women and newborns when done without medical indication. Crucially, inequalities in who receives CS exist, both within and across countries. Understanding factors driving increasing rates and inequalities of CS is imperative to optimise the use of this life-saving intervention. This study aimed to investigate trends of CS use and inequalities across sociodemographic characteristics in Indonesia over a 30-year period.MethodsSeven waves of the Indonesia Demographic and Health Survey were used to estimate trends and inequalities in CS from 1987 to 2017. Relative and absolute inequalities across a range of sociodemographic characteristics were estimated and trends in inequalities were assessed through changes in rate ratio and rate difference.ResultsThe proportion of facility-based births in Indonesia has increased in the past 30 years, coinciding with an increase in CS rate (CSR) (1991 CSR: 1.6% (95% CI 1.3 to 1.9); 2017 CSR: 17.6% (95% CI 16.7 to 18.5)). Higher rates of CS are observed mostly in Western Indonesia, while lower CSRs are observed in Eastern Indonesia. Inequalities of CSRs in Indonesia are observed across type of health facility (public/private), regions, places of residence, wealth quintiles and maternal education, with the highest CSRs in more affluent and educated groups. Widening absolute inequalities of CS are observed across all sociodemographic characteristics, except facility type, where CSR gaps between public and private facilities have closed on both relative and absolute scales.ConclusionThis study provides evidence of increasing trends in CSRs and widening absolute inequalities in CSRs across different sociodemographic groups of women in Indonesia. The context of increasing CSRs across society, however, may have resulted in more stable relative inequalities. Improving understanding of the drivers of these trends in Indonesia and, particularly, of women’s and providers’ perspectives and preferences for childbirth, should be prioritised to optimise the use of CS.