Zachary John Lemnios (born February 21, 1955) is an American scientist, executive, and engineer who has worked in government, industry, and academia.

[7] He also completed post graduate courses, including the Harvard Kennedy School of Government Program for Senior Executives in National and International Security (NIS).

[13] He joined the Information Processing Technology Office (IPTO) in April 2002, and was influential in the creation of the Personalized Assistant that Learns program.

[16] Lemnios was confirmed as Assistant Secretary of Defense for Research and Engineering by the Senate on June 19, 2009, and he was sworn in on July 2, 2009.

[30] He was selected by the Department of Defense to be one of the USA Science and Engineering Festival's Nifty Fifty Speakers to speak about his work and career to middle and high school students in October 2010.