Ammonia is gaining attention as an efficient hydrogen energy carrier and a decarbonized fuel. In Japan, the development of technologies to use ammonia as a fuel began in the 2010s, focusing on power generation and industrial heating systems. Today, its application is being explored across various sectors worldwide. For gas turbine power generation, IHI has developed a 2 MW gas turbine capable of operating on 100% liquid ammonia and is conducting long-term durability tests within a power generation package system. The application of this technology to large gas turbines is also underway. In the field of boiler thermal power generation, ammonia co-firing technology with a 20% ammonia fuel ratio has been developed and successfully demonstrated in a 1000 MW commercial power plant. This paper introduces the current status and prospects of ammonia firing power generation technologies.