The Ythan Estuary (Scottish Gaelic: Inbhir Eithein) is the tidal component of the Ythan River, emptying into the North Sea 19 kilometres (12 mi) north of Aberdeen, Scotland. The estuary’s tidal action extends a 7 kilometres (4.3 mi) inland and has characteristic widths of between 250 metres (820 ft) and 780 metres (2,560 ft). Besides the tidal channel there are interfaces to the upland dunes including mudflats, sand beaches and shingle flats. Reaches of salt marsh occur, but they are primarily near the Waterside Bridge (crossing of the A975 road) and the mouth of the Tarty Burn, a small tributary river. Based upon the habitat of the moorland bordering the east of the Ythan River near the mouth, this estuary is the most significant coastal moorland in the northern United Kingdom.