John Marshall Mitnick (born May 8, 1962) is an American lawyer who served as General Counsel for the United States Department of Homeland Security.

[2] From 2001 to 2002, he served as a counsel to the assistant attorney general of the Antitrust Division within the United States Department of Justice.

[3] From 2002 to 2004, he served as an associate general counsel for science and technology at the United States Department of Homeland Security.

[5] He was fired as DHS general counsel on September 17, 2019, reportedly because he had resisted illegal policies and actions pushed by White House Senior Advisor Stephen Miller.

[13] He also joined over 70 former senior Republican national security officials in issuing a statement, initially released on August 20, 2020, critical of Donald Trump and endorsing Joe Biden.