Hydrogen is the most promising alternative to fossil energy. Globally, hydrogen is getting attention from policymakers to lower greenhouse gas emissions. Many countries are focusing on decarbonizing the transport sector. Hydrogen-fueled internal combustion engines are under focus from engine manufacturers, especially for heavy-duty transport vehicles. Hydrogen-fueled engines do not emit particulate matter, carbon monoxide, carbon dioxide, and volatile organic compounds. However, it highly depends on the feedstocks used for hydrogen. The only challenge for engine manufacturers is to control the nitrogen oxide emissions. The after-treatment can tackle this issue and lower the nitrogen oxide emissions, also almost eliminate it subjected to engine operating conditions. Battery-electric vehicles would only be limited to two-wheelers, three-wheelers, and personal cars. Hydrogen engines will primarily drive the buses and heavy-duty trucks. Shortly, hydrogen will be the preferred choice for fueling construction machinery, agriculture machinery, and non-road applications. This book covers the technologies used for hydrogen production, recent advancements in hydrogen-fueled internal combustion engines, and various novel fuel injection strategies for enabling knock-free hydrogen engine combustion.