Derbyhaven is a hamlet near Castletown in the southern parish of Malew, connecting the Langness Peninsula to the rest of the island.
In the 17th century it was a significant port. The then Lord of Mann, James, 7th Earl of Derby, had the fort on nearby St Michael's Isle (Fort Island) rebuilt in 1645 (Henry VIII built the original fort in 1540) to protect Derbyhaven from the parliamentarians in the English Civil War. Later, in the 18th century, the fort served as a lighthouse.
Derbyhaven has a plaque commemorating the Battle of Ronaldsway, in which a Manx revolt led by Godred Magnusson was utterly crushed by Scottish forces in 1275.