The invention relates to a lock, in particular for a door or opening element of a motor vehicle. In order to avoid the unplanned opening of the lock in the event of a crash, the invention proposes a lock with a locking mechanism comprising a rotary latch, a pawl for locking the rotary latch in a detent position, preferably a blocking lever for blocking the pawl in the detent position and a release lever for opening the locking mechanism, in particular by lifting the blocking lever out of the blocking position. The lock is provided with a rotation-lock device, by means of which an opening process of the locking mechanism caused by momentum or an impact can be prevented or blocked.