Miller joins from USA Interactive, where he was president and chief executive of its Information and Services unit.
He replaces Robert Pittman, who left the company recently, having been parachuted in to try to turn the online unit around. It has been suffering badly at the hands of the advertising downturn.
AOL Time Warner chief executive Richard Parsons said: "Jon is absolutely the right person to lead America Online into its next stage of growth. Jon's success in building consumer-driven businesses online and offline has given him the right blend of expertise and experience to revitalise America Online."
While at USA Interactive, Miller oversaw its Ticketmaster, Citysearch and Match.com businesses, as well as the USA Travel Group, which comprises HRN, USA Travel Channel and Expedia.com.
Prior to USA Interactive, he spent four years through to 1997 with Viacom at its Nickelodeon/MTV Networks operations, where he headed up international activities. He has also worked for the National Basketball Association.
Miller will be one of the first AOL outsiders to run the company. In the past, it has been headed by a closely knit group of long-time staffers.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .