**Abstract**

Over the past few decades, Ru catalyzed transfer hydrogenation (TH) and asymmetric transfer hydrogenation (ATH) reactions of unsaturated hydrocarbons, imine, nitro and carbonyl compounds have emerged as economic and powerful tools in organic synthesis. These reactions are most preferred processes having applications in the synthesis of fine chemicals to pharmaceuticals due to safe handling as these do not require hazardous pressurized H2 gas. The catalytic activity and selectivity of Ru complexes were investigated with a variety of ligands based on pincer NHC, cyclophane, half-sandwich, organophosphine *etc*. These ligands coordinate to Ru center in a proper orientation with a labile group replaced by H-source (like methanol, isopropanol, formic acid, dioxane, THF), which facilitate the *β*hydrogen transfer to generate metal hydride species (Ru-H) and produce desired reduced product. This chapter describes the recent advances in TH and ATH reactions with homogeneous and heterogeneous Ru catalysts having different ligand environments and mechanistic details leading to their sustainable industrial applications.

**Keywords:** ruthenium, transfer hydrogenation/asymmetric transfer hydrogenation, homogeneous, heterogeneous catalysts, mechanistic studies
