Harrington succeeds Thomas Bjorn, who captained Europe to a dominant win over the United States in Paris in 2018.
The 47-year-old has a wealth of PGA Tour and Ryder Cup experience. Harrington is a three-time major champion and has served as an assistant captain for Europe at the last three events. He also participated as a player on six occasions between 1999 and 2010, winning four times.
The 2020 tournament will be hosted at Whistling Straits in Wisconsin.