Michael Douglas Griffin (born November 1, 1949 in Aberdeen, Maryland) is an American physicist, aerospace engineer and the former Administrator of NASA, from April 13, 2005 to January 20, 2009. As the chief of America's space agency, Dr. Griffin oversaw such areas as the future of human spaceflight, the fate of the Hubble telescope and NASA's role in understanding climate change. Dr. Griffin, who has a heavy academic background, was named eminent scholar and a professor of mechanical and aerospace engineering at The University of Alabama in Huntsville in April 2009. He had previously worked at NASA including as Associate Administrator for Exploration. When he was nominated as NASA chief, Dr. Griffin was working as the head of the Space Department at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. While he describes himself modestly as "a simple aerospace engineer from a small town," Griffin has held several high-profile political appointments. In 2007, he was named for the TIME 100, the magazine's list of the 100 most influential people.

Dr. Griffin's appointment was associated with a significant shift in the direction of the agency. He began signaling intended changes at his Senate confirmation hearing (see current plans for NASA below).

In 2004 testimony to Congress on the future of human spaceflight, he stated, "for me the single overarching goal of human space flight is the human settlement of the solar system, and eventually beyond. I can think of no lesser purpose sufficient to justify the difficulty of the enterprise, and no greater purpose is possible." In his testimony he also advocated heavy-lift launch capabilities, development of space qualified nuclear power systems, in situ resource utilization, and cost-effective medium-size transport to low Earth orbit.