The Workshop on Celtic Seas Aquaculture Overview (WKCSAO) was established to assemble and synthesize aquaculture related data and information from the Celtic Seas ecoregion to in form the Celtic Seas ecoregion aquaculture overview. The Celtic Seas ecoregion comprises much of the UK and all Ireland. Aquaculture is practised in all coastal waters. Both intertidal and subtidal waters are used for aquaculture. In the UK, aqua culture regulation and policy are devolved to the four countries: England, Scotland, Wales, and Northern Ireland. In addition to Ireland, there are five separate countries with potentially diverse aquaculture policy drivers and regulatory frameworks within the Celtic Seas ecoregion. Marine aquaculture production within the ecoregion is dominated by finfish, largely produced in Scotland. However, molluscs dominate in the other countries - Ireland, Northern Ireland, Eng land, Wales, and the Channel Islands. Seawater aquaculture is currently focused on 4 main spe cies that have all been farmed for > 40 years: Atlantic salmon, mussels (Mytilus spp.), Pacific cupped oyster and rainbow trout. In Ireland and the UK, small production units (< 5 employees) predominate. However, in both countries, more capital-intensive operations (i.e. finfish sector and larger shellfish farms) tend to operate multiple production units and will employ more people. Of note, the employment status (based upon FTEs) is more stable for the finfish sector than shellfish sector, which comprises larger proportion of part-time employment. While the overall employment is considered modest, the importance of these (even part-time) roles in more isolated rural areas is acknowledged. Environmental monitoring of aquaculture is primarily focused on finfish culture practices in all countries where impacts on habitats and wild salmonids are considered. Monitoring of shellfish culture practices are primarily focused upon food safety considerations, e.g. biotoxin and faecal coliform analysis. All species are subject to extensive animal health regulations that are wide ranging and derives primarily from EU legislation. In common with many production areas the primary environmental impacts relate to interfer ence on habitats and species. More specifically, for finfish culture, sea lice, genetic introgression from escaped farmed salmon and disease transmissions from salmon farms are considered as threats to wild salmon. Impacts on overwintering shore birds has been described in relation to intertidal culture operations (oysters and clams). Other environmental interactions considered include emissions of dissolved nutrients, particulate organic matter, pollutants and therapeu tants. A number of case studies are presented where likely interactions among social, economic and ecological drivers and presented solutions to avoid conflict are presented including open com munication among all stakeholders, wider socio-economic consideration and filling knowledge gaps in environmental interactions. A number of issues are identified which may affect aquaculture development and are considered common across the ecoregion. The geopolitical constraints to trade imposed by Brexit is of note. Delays and potential legal challenges associated with licencing decisions. Of particular concern are the potential effects of climate change and subsequent follow-on effects relating to disease, for example, in culture stock