Reports, images, GIS and gridded products describing the Palaeozoic geology and conventional petroleum in and around the Mid North Sea High (Quadrants 25-44). Covering a large area of the Central North Sea from the Forth Approaches to the northern side of the Southern North Sea, the focus is on Devonian and Carboniferous rocks. The peer-reviewed products were produced for the 21CXRM Palaeozoic Project by BGS for DECC/OGA, Oil and Gas UK and oil company sponsors between November 2014 and May 2016, to improve regional digital datasets and knowledge of the underexplored Palaeozoic petroleum systems, and to stimulate exploration. The petroleum systems analysis was based on new interpretations of extensive well, seismic, gravity-magnetic and source rock datasets, integrated with petrophysical studies, basin modelling and UK onshore knowledge. Released data were collated and interpreted, and interpretations of unreleased data were included with agreement of the data owners. Unreleased raw data is excluded, as is the UK Government Seismic data released in 2016. The datasets are applicable for use at scales between 1:750,000 to 1: 3,000,000.