An updated map of peat extent for Wales has been developed by the UK Centre for Ecology and Hydrology, with support from the British Geological Survey and Natural Resources Wales in support of the Glastir Monitoring & Evaluation Programme, commissioned by the Welsh Government. This map represents a considerable advance on previous attempts to map the deep peat resource of Wales and yields a significantly larger estimate than that based on the Soil Survey of England and Wales alone. This new map highlights the wide distribution of peatlands across much of Wales, with large areas of upland blanket bog in North east and North-central Wales (Migneint, Berwyn) and central Wales (Cambrian Mountains), as well as smaller areas of upland peat in and around the Brecon Beacons National Park. The new unified map also provides a much more detailed picture of the distribution of deep peat in the lowlands, many areas of which retain significant biodiversity interest. The Glastir Monitoring & Evaluation Programme was set up by the Welsh Government in 2013 to monitor the effects of the Glastir agri-environment scheme on the environment and ran from 2013 to 2016. Full details about this dataset can be found at https://doi.org/10.5285/58139ce6-63f9-4444-9f77-fc7b5dcc00d8