Hewson earned her bachelor of science in business administration and a master of arts in economics from the University of Alabama. She joined Lockheed Martin in the industrial engineering section in 1983. She became executive vice president of the company's Fort Worth, Texas-based aeronautics division. In 2008 she moved to the head the Systems Integration unit in Owego, New York and in 2010 became executive vice president of the Electronics Systems division. She was elected to the company's board of directors in 2012. She became CEO in January 2013 shortly after the retirement of former CEO Robert Stevens and the sudden resignation of his successor, Chris Kubasik, over ethics concerns.
Hewson serves on the boards of directors for DuPont and Sandia National Laboratories. She is also a member of the University of Alabama’s President’s Cabinet and also serves on the Board of Visitors of the Culverhouse College of Business, to which she and her husband have pledged a $15 million donation. She also serves on the Association of the United States Army Council of Trustees. In 2019 Hewson was inducted into the Alabama Business Hall of Fame.
- Diel, Stan (November 9, 2012) "University of Alabama grad appointed CEO of Lockheed Martin." The Birmingham News
- "Marillyn Hewson" (June 2, 2018) Wikipedia - accessed September 24, 2018
- Beahm, Anna (July 31, 2018) "Marillyn Hewson gives $15 million to UA Culverhouse College of Business." The Birmingham News
- Flanagan, Ben (September 24, 2018) "Alabama alum Marillyn Hewson named most powerful woman in business by Fortune." The Birmingham News
- Marillyn Hewson at lockheedmartin.com