Abstract: A manhole cover lock is provided employing two units diametrically situated and extending through openings in the manhole cover. The units engage a projection of the manhole cover housing to prevent the removal of the manhole cover when the units are in position. The units comprise a cylindrical body having a yoke at one end, a locking plate pivotally mounted in the yoke, with a flanged face opposite the yoke, and having a central recess. Extending through the body is an eccentric bore, in which a rod is housed, cooperating with said locking plate to provide a dog lock. A threaded bolt having a keyed head is threaded into a threaded axial bore in said body to prevent axial movement of said rod. An alternate embodiment of the threaded bolt includes modification of the head of the threaded bolt to allow the head to receive a special wrench for firmly tightening the threaded bolt thereby additionally securing the manhole lock in position.