The transportation sector is heavily dependent on internal combustion engines and will continue to remain so. However, the fuels would undergo transition. Depletion of petroleum reserves and the paradigm shift towards decarbonization has turned ammonia into a lucrative fuel for internal combustion engines. Carbon free nature, high energy density, low cost, presence of existing supply infrastructure, etc. are highlighting features that make ammonia a superior fuel. However, like any other fuel, it too has certain disadvantages that need to be addressed. High nitrogen oxide emissions and unburnt ammonia are the two broad challenges for ammonia as a fuel which can be overcome by regulating the combustion process. Thus, there is need to understand the fundamentals of ammonia combustion in detail and fine-tune the combustion process for widespread use. This chapter would help in understanding details of the ammonia combustion/oxidation process that would in turn help in achieving greenhouse gas emission targets in the near future.