Nowadays, hydrogen (H2) is mainly used as a raw material in chemical industries. In the future, it will also become a significant type of fuel due to the advantages of reduction in greenhouse gas emission, enhanced energy security, and promoted energy efficiency. To meet the future demand, sufficient H2 production in an environmentally and economically benign manner is a major challenge. This chapter provides an overview of H2 production pathways from fossil fuels, renewable resources (mainly biomass), and water. H2 production via calcium-looping and chemical-looping processes is also highlighted. The research activities, breakthrough, and challenges of various H2 production technologies are discussed. H2 from fossil fuels accounts for 96% of the total production around the world. Steam methane reforming, oil reforming, and coal gasification are the most common methods, and they are all commercially available. However, H2 generated from fossil fuels is nonrenewable, and in situ CO2 capture measures are essential. H2 produced from biomass is renewable and CO2 neutral. Biomass thermochemical processes such as pyrolysis and gasification are widely investigated and expected to be economically competitive with steam methane reforming. However, research on biomass biological processes such as photolysis, dark fermentation, photo-fermentation, etc. is still in laboratory scale, and practical applications of these technologies need further demonstrations. H2 from water splitting is also attractive because water is widely available and very convenient to use. However, water-splitting technologies including electrolysis, thermolysis, and photoelectrolysis are more expensive than conventional large-scale H2 production technologies using fossil fuels. Considering the development of renewable energies, water-splitting technologies with decreased capital and operation costs as well as promoted efficiency are expected to play a significant role in future H2 economy. Calcium looping and chemical looping have unique advantages of in situ CO2 capture that is of significance for H2 production from fossil fuels. Either semi-industrial or pilot scale test has been conducted for these technologies. Developing low-cost, recyclable, efficient looping materials and accelerating large-scale demonstration projects are the key drivers to their commercial applications.