Harmonizing data (achieving or improving inferential equivalence of data collected by separate studies) can be required in epidemiological research but is methodologically and technically challenging. Data collected by separate studies are typically heterogenous, and decisions on if and how to process data must be made, executed accurately, and documented in a transparent manner. Rmonize is an R package developed by Maelstrom Research to address some of the key challenges in this process and facilitate streamlined, reusable, and well documented harmonization pipelines.