In a recent count of cohort studies in Europe capturing information on occupation and/or occupational exposures, we estimated that there are more than 60 major studies with some type of occupational information that enrolled over 30 million persons. With few exceptions there have been no large-scale analyses systematically combining cohorts from this extraordinary resource. We present the development of an inventory of cohorts with occupational information in Europe and internationally and describe the online interactive tool with detailed information on existing cohorts. The OMEGA-NET inventory can be accessed at http://occupationalcohorts.net/ includes cohorts, case-control studies nested within cohorts and intervention studies that are active or can substantiate that their data are potentially accessible; that include data on occupation and/or industry or at least one occupational exposure; and that have at least one follow-up, either already conducted or planned. We expect that this open access inventory will be an important prerequisite for use of this resource of existing studies for research and policy development.