AbstractPhosphorene is a new 2D material composed of a single or few atomic layers of black phosphorus. Phosphorene has both an intrinsic tunable direct bandgap and high carrier mobility values, which make it suitable for a large variety of optical and electronic devices. However, the synthesis of single‐layer phosphorene is a major challenge. The standard procedure to obtain phosphorene is by exfoliation. More recently, the epitaxial growth of single‐layer phosphorene on Au(111) was investigated by molecular beam epitaxy and the obtained structure described as a blue phosphorene sheet. In the present study, large areas of high‐quality monolayer phosphorene, with a bandgap value equal to at least 0.8 eV, are synthesized on Au(111). The experimental investigations, coupled with density functional theory calculations, give evidence of two distinct phases of blue phosphorene on Au(111), instead of one as previously reported, and their atomic structures are determined.