Composite indicators (CIs) are aggregations of indicators that aim to measure complex, multidimensional and typically socio-economic concepts such as sustainable development (Conceição, 2020), innovation (Dutta et al., 2020), globalisation (William Becker et al., 2021), gender equality (Equal Measures 2030, and many more. CIs are very widely used in policymaking, by international organisations, and they are equally well-covered in academic literature (El Gibari et al., 2019;David Lindén et al., 2021;Stefana et al., 2021). They are often used to rank and benchmark countries or regions to help direct policy making, but are also frequently used for advocacy (Cobham et al., 2015).The COINr package, introduced in this article, aims to provide a harmonised development environment for composite indicators that includes all common operations from indicator selection, data treatment and imputation up to aggregation, presentation of results and sensitivity analysis. COINr enables development, visualisation and exploration of methodological variations, and encourages transparency and reproducibility.