Catalytic alkene hydrogenation is a powerful method that has been widely used in the syntheses of valuable products ranging from commodity chemicals to pharmaceuticals. Hydrogenation has also been a key strategy for selectively introducing heavy hydrogen isotopes to small molecules, a key strategy for metabolism studies and even the synthesis of "heavy drugs," where the hydrogen isotope is a key element of the active pharmaceutical ingredient. Traditional hydrogenations with pressurized H 2 gas are atom economic but often require complex reaction setups or expensive metal catalysts. Further, use of diatomic hydrogen necessarily limits the ability to incorporate different hydrogen isotopes at each alkene position, with H 2 , D 2 , and T 2 each resulting in compete labeling of the alkene. In response to these challenges, a recent and growing movement has sought to develop transfer hydrogenation methods using non-H 2 hydrogen sources and earth abundant element catalysts to simplify reaction operation. Excitingly, recent developments have delivered transfer hydrogenations that proceed using cooperative hydrogen donor reagents, permitting the controllable incorporation of different hydrogen isotopes at each position of the alkene via reagent control. In this Digest, we disclose recent advances in Earth-abundant metal-catalyzed cooperative transfer hydrogenation of alkenes with various combinations of two distinct transfer hydrogen reagents as non-H 2 hydrogen sources.