Michael D. Griffin, American physicist and engineer
Michael Douglas Griffin (born November 1, 1949) is an American physicist and aerospace engineer who served as the Under Secretary of Defense for Research and Engineering from 2018 to 2020. He previously served as Deputy of Technology for the Strategic Defense Initiative, and as Administrator of NASA from April 13, 2005, to January 20, 2009. As NASA Administrator Griffin oversaw such areas as the future of human spaceflight, the fate of the Hubble telescope and NASA's role in understanding climate change. In April 2009 Griffin, who has an academic background, was named eminent scholar and a professor of mechanical and aerospace engineering at the University of Alabama in Huntsville.

Griffin had worked at NASA prior to serving as NASA Administrator, including as Associate Administrator for Exploration. When he was nominated as NASA chief, he was head of the Space Department at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. While he describes himself as a "simple aerospace engineer from a small town", Griffin has held several high-profile political appointments. In 2007 he was included in the TIME 100, the magazine's list of the 100 most influential people.

Griffin's appointment as Administrator was associated with a significant shift in the direction of the agency. He began signaling intended changes at his Senate confirmation hearing.