• Rahul Prasad Singh, 
• Priya Yadav, 
• Indrajeet Kumar, 
• Ajay Kumar 
• Rajan Kumar Gupta 

Energy security is a major concern for economic strength worldwide because of fossil resource depletion and rising costs. The synthesis of biohydrogen from cyanobacteria is a viable alternative clean and renewable energy source with significant viable potential. Cyanobacteria are highly relevant and valuable as prospective hydrogen producers because they produce hydrogen from water due to solar energy conversion. Furthermore, cyanobacteria have high photosynthetic efficiency and produce a large amount of biomass, which is used as a fourth-generation feedstock to produce biohydrogen. The yield of cyanobacterial biohydrogen has been improved in various ways with limited information in a systematic way. That’s why the current state of research in the field of cyanobacterial hydrogen production enhancement is discussed with earlier published reports in this chapter. The major aim of this chapter is to discuss cyanobacterial hydrogen production, characteristics and roles of nitrogenase and hydrogenase enzymes concerned with hydrogen production, the various mechanisms of hydrogen production, recent metabolic pathway developments, modern photobioreactor efficiency, new cyanobacterial molecular genetic engineering and synthetic cyanobacterial biology. Finally, the major limitations to more efficient cyanobacterial hydrogen production and improvements for future commercialisation are also discussed.