<p>High-performance thermoelectric materials are typically narrow-band gap semiconductors. Here, by decoupling charge and heat transport in BaZrS₃ with a band gap of about 1.9 eV, we made the emerging chalcogenide perovskite a high-performance thermoelectric material with only earth-abundant elements. Our first-principles calculations indicate that the high ionicity of BaZrS₃ renders the electrons to propagate mainly through the Zr-4d orbitals, so that isovalent alloying Se on S sites minimally affects its charge transport while effectively suppressing lattice thermal conductivity. Using a flux-assisted solid-state method, we synthesized single-phase BaZrS_{3(1−<i>x</i>)}Se_3<i>x</i> samples with 0 ⩽ <i>x</i> ⩽ 0.25. As an indicator of decoupled charge and heat transport, the electron mobility is found barely degraded with increasing Se content, while the thermal conductivity is significantly reduced from 2.07 to 0.99 W m⁻¹ K⁻¹ at room temperature. This results in a record-high <i>ZT</i> of 0.81 at 750 K, a value never achieved for materials with band gaps greater than 1.5 eV, and the highest among all perovskite materials. Our work not only underscores the potential of wide band gap semiconductors as highperformance thermoelectric materials, but also demonstrates the strategy of decoupling the charge and heat transport for enhancing their thermoelectric performance.</p>