The Iodide in the Ocean project contains data from a combination of laboratory experiments, field measurements and ocean and atmospheric modelling from three cruises as well as worldwide sea surface measurements from 1967-2018 from published manuscripts, published and unpublished data supplied by the originators themselves or provided by repositories. The project brings together marine and atmospheric scientists to address uncertainties in the marine iodine flux and associated ozone sink. Specifically, it aims to quantify the dominant controls on the sea surface iodide distribution and improve parameterisation of the sea-to-air iodine flux and of ozone deposition. Iodide, iodate and total iodine concentrations were measured on three cruises: BOBBLE, June to July 2016 in the Bay of Bengal, Sagar-Kanya33 in September 2016 in the Arabian Sea and ISOE9 in January to February 2017 in the Indian and Southern Oceans. Samples were taken from Niskin bottles on conductivity-temperature-depth (CTD) profilers. Laboratory experiments consisted of phytoplankton cultures to measure rates of iodate incorporation and iodide production. This project was carried out by Lucy Carpenter (PI), Claire Hughes (Co-PI), Liselotte Tinel, and Helmke Hepach at York University, Mark Evans (Co-PI) at the University of Edinburgh. It was funded by the NERC Discovery Science project Iodide in the ocean: distribution and impact on iodine flux and ozone loss (parent grant reference NE/N009983/1 with child grants NE/N009444/1 and NE/N01054X/1 led by Stephen Ball and David Stevens respectively).