Great Britain supports internationally important numbers of wintering waterbirds, and accurate population estimates are essential for conservation assessment and site designation. Updated estimates are presented here for 99 species or populations, 65 of which have been newly revised using data from the Wetland Bird Survey (WeBS), the Goose and Swan Monitoring Programme (GSMP), the Non-Estuarine Waterbird Survey (NEWS), the Heronries Census, and other sources. Estimates generally represent the mean peak wintering population from 2017/18 to 2022/23, excluding 2020/21 owing to reduced coverage during the Covid-19 pandemic. Methodological refinements include an updated stratification framework distinguishing estuarine, coastal and inland habitats, and revised scaling of NEWS data. The total wintering waterbird population in Great Britain is estimated at 12.8 million individuals – unchanged from Frost et al. (2019) – but with notable shifts within species groups. Estuarine waders have increased, while several duck and goose populations have declined, including Bewick’s Swan Cygnus columbianus, Pink-footed Goose Anser brachyrhynchus and Eurasian Teal Anas crecca. Conversely, Whooper Swan Cygnus cygnus, Little Egret Egretta garzetta and non-migratory goose populations have continued to increase. The results highlight the continuing value of coordinated long-term monitoring, the need to repeat NEWS and expand offshore coverage, and the importance of maintaining robust population estimates for national and international conservation reporting.