Allonby Bay is a crescent-shaped bay of the Solway Firth on the north-western shore of Cumbria, United Kingdom. The bay is approximately five-and-a-half miles (nine kilometres) across. Its northern point is at Dubmill, between the village of Mawbray and the hamlet of Salta, and its southern end is just to the north of Maryport, near the village of Crosscanonby. The B5300 coast road follows the shoreline of Allonby Bay, running between Silloth-on-Solway in the north and Maryport in the south.