The paper investigates a previously unknown phase of phosphorus, referred to as "blue phosphorus," which shares a layered structure and high stability with black phosphorus. Blue phosphorus exhibits a hexagonal in-plane structure and bulk layer stacking similar to graphite but displays a wide fundamental band gap, exceeding 2 eV. This structure is predicted to be stable and easily exfoliable into quasi-2D structures suitable for electronic applications. The authors use *ab initio* density functional theory (DFT) calculations to study the equilibrium structure, stability, and electronic properties of blue phosphorus. They find that the transformation from black to blue phosphorus can occur through the introduction of dislocations in black phosphorus, and discuss possible synthesis methods. The study highlights the potential of blue phosphorus as a promising material for post-graphene 2D electronics due to its high carrier mobility and significant band gap.The paper investigates a previously unknown phase of phosphorus, referred to as "blue phosphorus," which shares a layered structure and high stability with black phosphorus. Blue phosphorus exhibits a hexagonal in-plane structure and bulk layer stacking similar to graphite but displays a wide fundamental band gap, exceeding 2 eV. This structure is predicted to be stable and easily exfoliable into quasi-2D structures suitable for electronic applications. The authors use *ab initio* density functional theory (DFT) calculations to study the equilibrium structure, stability, and electronic properties of blue phosphorus. They find that the transformation from black to blue phosphorus can occur through the introduction of dislocations in black phosphorus, and discuss possible synthesis methods. The study highlights the potential of blue phosphorus as a promising material for post-graphene 2D electronics due to its high carrier mobility and significant band gap.