We report the observation of the decay B-0 ->pi(0)pi(0), using a 253 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) collider. The measured branching fraction is B(B-0 ->pi(0)pi(0))=(2.3(-0.5-0.3)(+0.