Jeffrey Lane Hephner is an American actor, best known for the role of Jeff Clarke, first on the NBC television series Chicago Fire and then on its sister show, Chicago Med. More recently, he co-starred with Jennifer Garner in the action thriller film Peppermint. He also appears in the 2016 National Geographic TV series MARS and the Apple TV+ original science fiction space drama series For All Mankind. In January 2019, he co-starred in the film An Acceptable Loss. Hephner has appeared in over 50 other films and television shows, including as Morgan Stanley Buffkin in the CW series Easy Money (2008–2009), and as Ben Zajac in the Starz political drama Boss (2011–2012). In 2015, he starred as the title character in the short-lived TNT action drama Agent X.