Belfast Lough in Northern Ireland like most estuarine systems in the UK and Europe once supported a prolific Ostrea edulis fishery. However, the oyster was considered locally extinct from the Lough by the early 1900s. Numerous ecological surveys of the over the next 100 years failed to document one living specimen. Recently, unsubstantiated sightings of solitary O. edulis along the Loughs intertidal were conveyed to the author. It was considered necessary to investigate these reports and as a result the presence of small assemblages of European flat native oysters was confirmed. Hypotheses as to why the oysters have returned unaided are discussed with the aim to investigate these at depth in the future.