Ionic hydrogenation reactions involve the use of a hydrogenating pair consisting of proton donors and hydride ions. The synthetic applications of this method for the non-catalytic hydrogenation of C=C, C=O, C=N multiple bonds, and of C-OH, C-Hal, etc. single bonds are described. 1. Hydrogenating Pairs 2. Reaction Conditions and Isolation of Hydrogenation Products 3. Preparation of Alkanes, Cycloalkanes, Alkylarenes and Their Derivatives 4. Preparation of Alcohols and Thiols 5. Preparation of Carbonyl Compounds 6. Preparation of Ethers by Ionic Hydrogenation of Aldehydes, Ketones, and Acetals 7. Ionic Hydrogenation of Derivatives of Sandwich Compounds of Transition Metals and of Organo-Cobalt Clusters 8. Preparation of Secondary Amines by Ionic Hydrogenation of Schiff Bases 9. Preparation of Compounds Containing Deuterium in a Predetermined Position 10. Hydrogenation of Heterocycles 11. Stereoselectivity of Ionic Hydrogenation