The invention relates to a portable lock having an unlocking motor, an authentication module for authenticating a user of the lock by which the unlocking motor can be actuated to unlock the lock on a successful user authentication, and having a transport security element that can be actuated by the user and whose actuation moves the lock into a transport security mode in which an unlocking of the lock is precluded. A further subject matter is a locking system comprising such a lock and a mobile end device by means of which a user of the lock can authenticate himself thereat. The invention furthermore relates to a method of unlocking a mobile lock.