On the basis of first principles calculations, we propose Pd₃P₂S₈ monolayer and bilayer, two-dimensional semiconductors, whose layered bulk parent crystals are experimentally reported, as promising photocatalysts for the solar-driven oxygen evolution reaction. The monolayer is kinetically and thermodynamically stable and shows a small cleavage energy of 0.35 J m⁻², suggesting that it can be prepared by exfoliation from its bulk material, and exhibits a direct band gap of 2.98 eV, which can be engineered by applying strain. The Pd₃P₂S₈ bilayer is an indirect band gap semiconductor with a slightly smaller band gap of 2.83 eV. The photoexcited holes generate favorable driving forces for promoting the specific solar-driven O₂ evolution reaction. The extraordinary electronic properties, pronounced light harvesting capability in the visible and ultraviolet regions and active surface sites render the Pd₃P₂S₈ monolayer and bilayer as compelling 2D materials with interesting application potential for photocatalytic and photoelectrocatalytic water splitting.