Hydrogen is considered as an important energy vector for the 21^st century and its production from renewable resources, like biomass-derived products, is one of the main challenges. On the other hand, glycerol, a byproduct of the biodiesel production, may turn out to be an environmental problem due to the large amount of glycerol generated worldwide. The production of hydrogen from glycerol is a promising route to alleviate this problem. This paper focuses on the conversion of glycerol to hydrogen through aqueous-phase reforming and steam reforming, by providing a comprehensive review of the catalysts used in these processes and examining the involved reaction mechanisms.