The forest fire model exhibits a percolation phase transition at critical density p_c ≈ 0.593 (site percolation on a square lattice). Below p_c fires die out quickly; above p_c they span the system. The growth/lightning ratio determines the fractal structure of the fire front. Near criticality, cluster sizes follow a power law with exponent τ = 187/91 (2D percolation universality class).