Milecastle 41, also known as Melkridge was a milecastle on Hadrian's Wall, grid reference NY73026705. There are no visible remains above ground but the milecastle can be made out by turf-covered banks outlined by robber trenches. The milecastle lies to the west if Caw Gap and a cottage, long removed, occupied the site of, and was built from, the materials of milecastle 41.

Milecastle 41 has 2 associated turrets, Turret 41A Caw Gap (grid reference NY72556688), and Turret 41B, Thorny Doors (grid reference NY72056683).

When milecastle 41A was excavated in 1912, it was believed that in the later Roman period, the turret was deliberately demolished, and the Wall rebuilt across its site, the remains of Turret 41A were consilidated in 1972 and can be seen as a 20cm ridge above ground. There are however no visible remains of milecastle 41B.