This dataset provides the location details of Environmental Change Network (ECN) sites from which data are collected. There are 12 terrestrial sites and 45 freshwater sites. Sites range from upland to lowland, moor land to chalk grassland, small ponds and streams to large rivers and lakes. ECN is the UK's long-term environmental monitoring programme. A wide range of integrated physical, chemical and biological variables which drive and respond to environmental change are collated, quality controlled and made freely available for scientific research. The data form an important evidence base for UK environmental policy development. ECN is a multi-agency programme sponsored by a consortium of fourteen government departments and agencies. These organisations contribute to the programme through funding either site monitoring and/or network co-ordination activities. These organisations are: Agri-Food and Biosciences Institute, Biotechnology and Biological Sciences Research Council, Cyfoeth Naturiol Cymru - Natural Resources Wales, Defence Science & Technology Laboratory, Department for Environment, Food and Rural Affairs, Environment Agency, Forestry Commission, Llywodraeth Cymru - Welsh Government, Natural England, Natural Environment Research Council, Northern Ireland Environment Agency, Scottish Environment Protection Agency, Scottish Government and Scottish Natural Heritage.