This document concerns the restoration of rivers, including their channels, riparian zones, and floodplains. The word ‘river’ is used as a generic term to describe permanently flowing and intermittent watercourses of all sizes, with the exception of artificial water bodies such as canals. Some aspects of landscape restoration beyond the boundaries of what are often considered typical river processes are also considered. This document focuses on ‘nature-based solutions’, which are ‘actions to protect, sustainably manage and restore natural or modified ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits’ (https://portals.iucn.org/library/sites/library/files/documents/2016-036.pdf). A clear framework of guiding principles to help inform the planning and implementation of river restoration work is provided. These principles are aimed both at individuals and organizations wishing to restore rivers, and stress the importance of monitoring and appraisal. This document makes reference to existing techniques and guidance, where these are appropriate and within the scope of this document. This document provides guidance on: – the core principles of restoration – the aims and overall outcomes of river restoration – the spectrum of typical approaches to river restoration (the ‘restoration mode’) with a focus on those that are nature-based and restore both physical and ecological aspects – identifying opportunities for restoration and possible constraints, with a focus on physical and natural rather than socio-economic aspects – the different scales of restoration and how restoration works across different catchments and landscapes – the importance of monitoring and appraising restoration work across the range of approaches and scales.