The country's top telecommunications regulator told a staff meeting of his decision Friday morning. His impending departure was reported Thursday by several news outlets.
Genachowski, 50, was appointed in 2009 and has hewed a middle line between the desires of public-interest groups and the telecom industry, which hasn't enamored him to either side.
His tenure has seen continued adoption of broadband and ever higher Internet connection speeds, especially on the wireless side, but consumer groups saw the approval of Comcast's acquisition of NBC as a mistake, while AT&T Inc. suffered a severe blow when its acquisition of T-Mobile USA was blocked.
His departure will follow that of Republican Robert McDowell, which leaves the five-member commission with a 2-1 Democratic majority until President Obama appoints a new chairman and commissioner.
Stifel Nicolaus analysts Christopher King and David Kaut said they believe the front-running candidate for next chairman is Tom Wheeler, a venture capitalist and former president of two major trade groups, for the cable and wireless industries.