Two-wheeler lock having an alarm function

A lock having an alarm function for a two-wheeler comprises a lock body and a securing hoop movable relative to the lock body between a securing position for securing the two-wheeler and an open position for releasing the two-wheeler. The lock body has a locking mechanism to selectively lock the securing hoop to the lock body in the securing position, and further comprises an alarm device for outputting an alarm signal. The locking mechanism can selectively be moved into an unlocked position, a locked position, or an alarm activation position, with the securing hoop being released for a movement into the open position in the unlocked position, with the securing hoop located in the securing position being locked at the lock body in the locked position, and with the alarm device being activated or being able to be activated by moving the locking mechanism into the alarm activation position.