<p>Thermoelectric materials directly convert thermal energy into electrical energy, demonstrating significant potential for energy and environmental applications. Ideally, high-performance thermoelectric materials should exhibit ultra-low lattice thermal conductivity and high charge carrier mobility akin to a phonon-glass electron-crystal. However, the strong coupling between electronic transport and phonon transport presents considerable challenges in enhancing thermoelectric performance, with the independence of lattice thermal conductivity being the key to decoupling these processes. This review emphasizes the critical role of low lattice thermal conductivity in enhancing the performance of thermoelectric materials. It begins by exploring the low thermal conductivity features arising from the intrinsic structures of these materials, including anharmonic structures and super-nanostructures. We then propose innovative strategies for tuning thermal conductivity through phase engineering. Additionally, we review recent advancements in defect engineering aimed at reducing lattice thermal conductivity in the thermoelectric field. Finally, we discuss emerging developments, applications, and challenges in the field of thermoelectric materials.</p>