This report on "Uncertainties in Ocean Colour Remote Sensing" summarizes the state of the knowledge on uncertainties related to ocean colour (OC) products and identifies ideas and recommendations to achieve significant progress on how uncertainties are quantified and distributed. The report starts with a presentation of terminology and concepts (Chapter 2). For a proper use of OC data, it is necessary to be aware of the potential problems and limitations associated with OC remote sensing products, and to identify the sources contributing to their uncertainties, from top-of-atmosphere (TOA) data to gridded products. This report makes a review of these factors (Chapter 3). Even though up to now very few OC products have been distributed with uncertainty estimates, a number of approaches to quantify OC product uncertainties have been proposed in recent years; providing a review of these methods and discussing their respective advantages appear particularly timely (Chapter 4). It is also necessary to discuss how information on uncertainty could be conveyed to user communities (Chapter 5) and to describe example requirements from these communities (Chapter 6). General recommendations are provided in the final chapter (Chapter 7).