Abstract: A chain saw safety guard is provided for protecting against accidental contact with the longitudinal side edges of a chain saw cutter bar. The safety guard includes a generally U-shaped guard member having two parallel guard rails which extend to the open end of the U and a cross-piece or cross-member at the closed end of the U. The guard is supported on the cutter bar at its forward or outermost end by means of a track on the bar and a follower coupled to the guard member. The guard rails are supported near the proximal end of the cutter bar on slidable supports which allow the rails to move longitudinally along the cutter bar to retract and expose the cutting edges of the saw. A telescoping version of the guard member, in which the guard rails telescope into a more compact configuration, is also disclosed. A movable track on the cutter bar, in the form of a longitudinal slot through the bar, helps cool the cutter bar.