River temperature is important for cold water adapted freshwater fish species, such as salmonids. Salmonids command a high economic, social, recreational and conservation value and are therefore frequently the focus of management. In recognition of the importance of river temperature, and against a backdrop of sparse data availability, the Co-ordinated Agenda for Marine, Environment and Rural Affairs Science (CAMERAS) prioritised the development of a strategically designed national river temperature monitoring network for Scotland to assess and predict the likely effects of climate change and inform mitigation strategies. The work undertaken for this thesis filled this research gap. Specifically, it delivered 1) a quality controlled national river temperature monitoring network (Scotland River Temperature Monitoring Network), 2) new and innovative statistical approaches for modelling river temperature, 3) improved understanding of the controls on large-scale variability in river temperature across Scotland, 4) characterised river temperature for Scotland, 5) identified rivers and regions that are likely to be most sensitive to climate change and 6) investigated the potential of riparian woodland to mitigate high river temperatures that are potentially damaging to Scotland's valuable freshwater fisheries. The outputs of this research have provided valuable management tools to river and fisheries managers and policy makers.