The morphodynamics of estuaries on the west coast of Donegal, north-west Ireland have been examined at the meso-scale (historical), short-term (years) and micro-scale (days) through the interpretation of past maps and aerial photographs and the regular field monitoring and quantitative assessment of morphological changes and associated climatic and marine conditions. Three estuaries were examined in detail: Gweebarra, Loughros Beg and Loughros More. The morphologically dynamic estuaries on the west coast of Ireland are characterised by constricted inlets, bound by large dune barriers and bedrock margins at the mouths of shallow estuarine basins comprising extensive inter-tidal sand flats and sinuous low tide ebb channels. The coastline is exposed to the high energy north Atlantic swell wave climate and a meso-tidal, semi-diurnal tide regime. The estuaries display similar patterns of morphological change over the meso-scale. Maximum morphological change is observed within the inlet region of the estuarine systems and the character of change is determined by inlet configuration. Furthermore, major changes in morphology are thought to be related to episodic high energy events. Dune barriers are the focus of storm induced erosion, both in terms of dune front recession and surface degradation and destabilisation. Open coast beaches are dissipative, whilst more sheltered pocket beaches have an intermediate morphodynamic character. Closer to estuary inlets, the inter-tidal region exhibits greater magnitudes and directions of change due to the influence of tidal currents in addition to the high wave energy climate, whilst the dune environments are subject to considerable storm induced recession. Within the estuarine basins, inter-tidal flats indicate accretional behaviour through flood-tidal current sediment transport. Vertical sedimentation rates of 0.05 – 0.16 myr-1 have been recorded. The sand dominated character of estuarine deposits indicates that sedimentation is from a coastal or marine source, not fluvial, and possibly augmented by the episodic release of sediment from the inlet dune systems. Micro-scale morphodynamics examined over the foreshore revealed that sediment transport increases significantly from the open coast environment toward the inlet region. This was attributed to the increased influence of tidal currents on sediment transport mechanisms. The morphodynamics observed at the various time scales indicate that the west Donegal estuarine systems can be described as mixed (tidal and wave) energy. Existing models defining estuarine systems do not effectively classify the Donegal estuaries due to the high wave and tidal energy nature of the coastline, in addition to the spatial variations in wave and tide dominance within the estuarine systems and the inherent geological boundaries within which the estuaries exist. Furthermore, the occurrence of significant high energy events is thought to be a critical factor in estuarine morphodynamics, in terms of releasing sediment from the large dune barrier deposits for progressive estuarine sedimentation and in promoting an overall erosional front within a period of near-negligible sea level changes. Such site specific character can not be summarised in terms of a universal model of estuarine morphodynamics.