The Indian Monsoon Data Assimilation and Analysis (IMDAA) project is a formal collaboration between the United Kingdom Met Office (UKMO), the National Centre for Medium Range Weather Forecasting (NCMRWF) and the India Meteorological Department (IMD). The project is funded by the Indian Ministry of Earth Sciences through the National Monsoon Mission. The principal aim of this 4 year project is to develop and run, for the first time, a long‐period high‐resolution regional reanalysis over the Indian subcontinent. The development has been completed and production runs are underway. The reanalysis will produce a consistent data set of high‐resolution fields for a wide range of atmospheric variables available from 1979 to 2018 (satellite era).