| Milefortlet 4 | |
|---|---|
 Fields by the Solway Firth, and the approximate site of Milefortlet 4 | |
  Location within Cumbria | |
| Type | Milecastle |
| Place in the Roman world | |
| Province | Britannia |
| Location | |
| Coordinates | 54°55′35″N 3°17′21″W / 54.926352°N 3.289258°W |
| County | Cumbria |
| Country | England |
| Reference | |
| UK-OSNG reference | NY17475983 |
Milefortlet 4 (Herd Hill) 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 4 has been located by archaeologists.