We describe the development and validation of a new near-global gridded marine humidity monitoring product, HadISDH.marine, from air temperature and dew point temperature reported by ships. Erroneous data, biases, and inhomogeneities have been removed where possible through checks for outliers, supersaturated values, repeated values, and adjustments for known biases in non-aspirated instruments and ship heights. We have also estimated uncertainty in the data at the grid box and regional level.