Abstract: A coupler for attaching a suppressor to a firearm flash hider. The coupler includes a main body, an inner collar, and an outer collar. The main body defines a through bore configured to closely receive the flash hider at one end and for the passage of the bullet at the other. The main body defines a first threaded portion proximate the central portion thereof, the threads being right-handed threads. The main body defines a sound suppressor attachment device at the second end thereof. The inner collar defines a through bore oriented coaxially thereto. A first end of the through bore is configured to receive the first end of the main body. Proximate the second end of the inner collar, the through bore defines a second inner diameter dimensioned to receive the firearm flash hider. The inner collar carries a plurality of locking fingers, each pivotally mounted on the inner collar via a pivot pin.