The Rapid Climate Change (RAPID) data set comprises a diverse collection of oceanographic and benthic observations, including profiles of temperature, salinity, dissolved gases and currents. The dataset also includes discrete measurements of plankton, stable isotopes, dissolved metals, chlorofluorocarbons (CFCs) and nutrients in the water column, sediment grain size parameters and geochemistry, and atmospheric concentrations of inorganic halogens. The RAPID data were collected from numerous locations in the North Atlantic, North Sea, Greenland and Europe via over 30 cruises between 2004 and 2008. Many of the oceanographic data resulted from an extensive mooring array in the North Atlantic devoted to monitoring the Atlantic overturning circulation. These mooring arrays are continuing to return data in the follow-on programmes, Rapid Climate Change - Will the Atlantic Thermohaline Circulation Halt? (RAPID-WATCH, 2008-2015) and RAPID - Atlantic Meridional Overturning Circulation (RAPID-AMOC, 2015 onwards) which will result in a decadal time series spanning the North Atlantic. RAPID, RAPID-WATCH and RAPID-AMOC aim to investigate and understand the causes of rapid climate change, with a primary (but not exclusive) focus on the role of the Atlantic Ocean thermohaline circulation. A Rapid Climate Change project office has been established at the National Oceanography Centre, Southampton. The cruise and mooring data are managed by the British Oceanographic Data Centre and are supplemented by atmospheric model output held at the British Atmospheric Data Centre (BADC).