The article presents a novel heterogeneous Ru–S catalyst that can tolerate multiple sulfur functionalities, including thioethers, thiophenes, sulfoxides, sulfones, sulfonamides, and sulfoximines, during the hydrogenation of quinolines. The catalyst was synthesized via hydrothermal methods and characterized using various techniques such as XPS, ICP-OES, TEM, and EDX. The chemoselectivity and sulfur resistance of the catalyst were demonstrated through a diverse substrate scope, showing high yields of 1,2,3,4-tetrahydroquinolines (THQs) while preserving other functional groups susceptible to reduction. The catalyst's ability to handle sulfur functionalities, including those with medicinal relevance, highlights its potential for the synthesis of complex structures in medicinal chemistry. The study also explores the recyclability of the catalyst, which showed minimal loss in activity after multiple reaction cycles. The versatility of the catalytic protocol is further demonstrated by downstream product modifications, such as Corey–Seebach-type umpolung reactions and SuFEx click reactions, highlighting the method's utility in creating complex chemical motifs.The article presents a novel heterogeneous Ru–S catalyst that can tolerate multiple sulfur functionalities, including thioethers, thiophenes, sulfoxides, sulfones, sulfonamides, and sulfoximines, during the hydrogenation of quinolines. The catalyst was synthesized via hydrothermal methods and characterized using various techniques such as XPS, ICP-OES, TEM, and EDX. The chemoselectivity and sulfur resistance of the catalyst were demonstrated through a diverse substrate scope, showing high yields of 1,2,3,4-tetrahydroquinolines (THQs) while preserving other functional groups susceptible to reduction. The catalyst's ability to handle sulfur functionalities, including those with medicinal relevance, highlights its potential for the synthesis of complex structures in medicinal chemistry. The study also explores the recyclability of the catalyst, which showed minimal loss in activity after multiple reaction cycles. The versatility of the catalytic protocol is further demonstrated by downstream product modifications, such as Corey–Seebach-type umpolung reactions and SuFEx click reactions, highlighting the method's utility in creating complex chemical motifs.