The ODIS "Catalogue of Sources" aims to be an online browsable and searchable catalogue of existing ocean related web-based sources/systems of data and information as well as products and services. It will also provide information on products and visualize the landscape (entities and their connections) of ocean data and information sources. It will contribute to the objectives of the Agenda 2030, and in particular the UN Decade for Ocean Science for Sustainable Development. The Catalogue is not an ocean database or metadata repository. The catalogue includes descriptive information such as the URL, title, description, language, point of contact, geographic scope, available technologies for machine-to-machine interaction, keywords, etc. and can be searched on many of these fields. The IODE network of NODCs has been collecting, managing and serving data for decades. This effort has yielded an extensive, but distributed and heterogeneous collection of data and information sources. Additionally, the low threshold for technical capabilities required to offer data and information over the Internet means that many of the hosted resources are not readily discoverable through NODCs, regional or international data and information systems ODIS will provide an online catalogue of (ideally) all online data/information sources (and, where possible, metadata on off-line sources as well). Many regional and international programmes and projects have developed online data/information services but there is currently no "one-stop shop" where users are offered an overview and/or common data/information discovery interface. There are currently 3090 sources (2172 are searchable) catalogued in the system.