Systems for universally locking a trigger of a firearm are provided that require authentication to transition the firearm to an unlocked state. In general, examples of the systems for universally locking a trigger of a firearm described herein are located in an interchangeable grip portion of the firearm or mounted to an accessory rail of the firearm. Embodiments of the system generally include trigger interference or blocking members to prevent actuation of the trigger until the authentication system has authorized the user to fire the firearm. Once the system is authenticated, embodiments of the system remain in an unlocked state while the user is grasping the firearm. When the user removes their hand from the firearm, embodiments of the trigger locking system automatically returns to a locked state, reducing or eliminating unauthorized use of the firearm.