Emerging rechargeable sodium-ion storage systems—sodium-ion and room-temperature sodium–sulfur (RT-NaS) batteries—are gaining extensive research interest as low-cost options for large-scale energy-storage applications. Owing to their abundance, easy accessibility, and unique physical and chemical properties, sulfur-based materials, in particular metal sulfides (MSx) and elemental sulfur (S), are currently regarded as promising electrode candidates for Na-storage technologies with high capacity and excellent redox reversibility based on multielectron conversion reactions. Here, we present current understanding of Na-storage mechanisms of the S-based electrode materials. Recent progress and strategies for improving electronic conductivity and tolerating volume variations of the MSx anodes in Na-ion batteries are reviewed. In addition, current advances on S cathodes in RT-NaS batteries are presented. We outline a novel emerging concept of integrating MSx electrocatalysts into conventional carbonaceous matrices as effective polarized S hosts in RT-NaS batteries as well. This comprehensive progress report could provide guidance for research toward the development of S-based materials for the future Na-storage techniques.