Milefortlet 12 (Blitterlees) was a Milefortlet of the Roman Cumbrian Coast defences. These milefortlets and intervening stone watchtowers extended from the western end of Hadrian's Wall, along the Cumbrian coast and were linked by a wooden palisade. They were contemporary with defensive structures on Hadrian's Wall. There is little to see on the ground but Milefortlet 12 has been located and excavated. The milefortlet is located close to the hamlet of Blitterlees, in the civil parish of Holme Low.