Trigger groups for striker-fired firearms have a firing pin assembly connected to a slide and operable to reciprocate between a rearward retracted position and a forward extended position, the firing pin assembly including a retention surface, a trigger assembly including a sear surface configured to selectively engage the retention surface to releasably restrain the firing pin assembly, the firing pin assembly being responsive to the trigger assembly to release from the retracted position to the extended position in response to movement of the trigger assembly from the forward trigger position to the rearward trigger position and to release from the retracted position to the extended position in response to movement of the trigger assembly from the rearward trigger position to the forward trigger position, the trigger assembly including a retainer movable between a clear position and a blocking position.