Two-dimensional (2D) ferroelectrics (FEs) with scale-free polarization provide a promising platform for next-generation nanoscale information technologies. Using first-principles calculations, we predict a 2D FE ${\mathrm{Ba}}_2{\mathrm{Sb}}_2{\mathrm{Se}}_4{\mathrm{F}}_2$ monolayer and demonstrate a concrete realization of 2D scale-free ferroelectricity, enabled by the weak coupling between the polar Sb–Se chains on the two surfaces of the monolayer. The unconventional polarization behavior in ${\mathrm{Ba}}_2{\mathrm{Sb}}_2{\mathrm{Se}}_4{\mathrm{F}}_2$ monolayer originates from two Sb–Se polarization chains that are effectively decoupled in both electronic structure and lattice dynamics. This decoupling enables independent dipole switching, such that the macroscopic polarization arises purely from the vectorial superposition of local molecular dipoles, giving rise to a well-defined scale-free FE response. The energy landscape contains multiple FE, antiferroelectric (AFE), and metastable intermediate states connected by low-barrier switching pathways. As a result, the monolayer supports eight reversible polarization states, offering a versatile platform for multilevel applications. Our findings expand the family of scale-free FEs and highlight monolayer ${\mathrm{Ba}}_2{\mathrm{Sb}}_2{\mathrm{Se}}_4{\mathrm{F}}_2$ as a promising candidate for multifunctional FE devices.

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• Antiferroelectricity
• Electronic structure
• Ferroelectricity
• Phase transitions
• 2-dimensional systems
• Ferroelectrics
• Density functional theory
• First-principles calculations