An ergonomic weapon sling includes an elongate strap having a preformed permanent curved shape adapted to conform to the anatomical contour of the user's body along an elongate area of contact between the strap and the body. First and second fasteners are carried on the strap for attaching to the forearm and stock of a rifle or shotgun. The sling is positionable in a carrying position in which the strap is positioned over a shoulder of the user and conforms to the contour of the user's torso, and is also positionable in an aiming position in which the strap conforms to the contour of an upper arm of the user and stabilizes the arm supporting the forearm of the weapon to aid the user in aiming the weapon.