Abstract: This invention is a well casing closure for closing and covering the top of a well casing extending above the surface of the ground. The invention is characterized by comprising a hollow cylindrical member closed on one end and open on the other end of such dimension as to fit over the top of the well casing and to provide a reasonably snug fit about the exterior of the casing; it is further characterized by utilizing an "O" ring or the like, for sealing between the interior of the closure and the exterior of the casing; additionally, a locking mechanism is incorporated so that the closure may be locked in place over the opening and only removed by one having a key to the lock.