Edward Casey O'Callaghan (born June 8, 1969) is an American attorney and former U.S. Department of Justice official. In his early career, O'Callaghan was an assistant U.S. attorney in the U.S. Attorney's Office for the Southern District of New York. He resigned to join John McCain's 2008 presidential campaign, where he was one of the became the public faces of the legal defense of McCain's running mate, Sarah Palin, against ethics charges related to her former brother-in-law (the "Troopergate" affair). From 2009 to 2011, he worked at the law firm Nixon Peabody, then from 2011 to 2017 he was a partner at the New York office of law firm Clifford Chance. In 2017, during the Trump administration, he became the principal deputy assistant attorney general of the U.S. Department of Justice Nation