A dual quantum spin Hall (QSH) insulator has been observed in a van der Waals monolayer of TaIrTe₄, arising from the interplay of its single-particle topology and density-tuned electron correlations. At charge neutrality, monolayer TaIrTe₄ exhibits a QSH insulator with quantized helical edge conductance, consistent with single-particle band structure calculations. Upon introducing electrons from charge neutrality, TaIrTe₄ shows metallic behavior in a small range of charge densities but quickly transitions into a new insulating state, likely due to a charge density wave (CDW) near van Hove singularities. This insulating state hosts a resurgence of the QSH state, marked by nonlocal transport and quantized helical edge conduction. The dual QSH insulator demonstrates a flat QSH band, offering a platform for exploring time-reversal-symmetric fractional phases and electromagnetism. The study reveals that TaIrTe₄ is a novel dual QSH insulator, combining a single-particle QSH state at charge neutrality with a correlated QSH state arising from enhanced correlations. The two QSH states can be switched by tuning carrier density via gating. Theoretical analyses suggest that the dual QSH state arises from the interplay of single-particle topology and CDW-induced correlations, with the CDW gap hosting nontrivial QSH states. The discovery of a dual QSH insulator provides a new method for creating topological flat minibands via CDW superlattices, which could be useful for exploring time-reversal-symmetric fractional phases.A dual quantum spin Hall (QSH) insulator has been observed in a van der Waals monolayer of TaIrTe₄, arising from the interplay of its single-particle topology and density-tuned electron correlations. At charge neutrality, monolayer TaIrTe₄ exhibits a QSH insulator with quantized helical edge conductance, consistent with single-particle band structure calculations. Upon introducing electrons from charge neutrality, TaIrTe₄ shows metallic behavior in a small range of charge densities but quickly transitions into a new insulating state, likely due to a charge density wave (CDW) near van Hove singularities. This insulating state hosts a resurgence of the QSH state, marked by nonlocal transport and quantized helical edge conduction. The dual QSH insulator demonstrates a flat QSH band, offering a platform for exploring time-reversal-symmetric fractional phases and electromagnetism. The study reveals that TaIrTe₄ is a novel dual QSH insulator, combining a single-particle QSH state at charge neutrality with a correlated QSH state arising from enhanced correlations. The two QSH states can be switched by tuning carrier density via gating. Theoretical analyses suggest that the dual QSH state arises from the interplay of single-particle topology and CDW-induced correlations, with the CDW gap hosting nontrivial QSH states. The discovery of a dual QSH insulator provides a new method for creating topological flat minibands via CDW superlattices, which could be useful for exploring time-reversal-symmetric fractional phases.