The present invention relates to a cutter guard for a rotating blade of a lawn mower, particularly for a robotic, self-guided or autonomous lawn mower. We describe a cutter guard for a rotatable blade of a robotic rotary lawn mower, the guard forming a cutting bowl in which said blade is mounted for rotation about a generally vertical axis； and wherein said guard comprises, a generally planar guard section surrounded by an arcuate section, transverse edges of which define an opening in said cutter guard, which in operation is pointed to the front of said lawn mower, to allow uncut grass to be accessed by the cutting blades, said arcuate section comprising a plurality of apertures.
