Leo Sidney Mackay Jr. (born August 15, 1961) is an American businessman, and a former deputy secretary of the United States Department of Veterans Affairs.

[1] Currently, he is senior vice president - ethics and enterprise assurance, serving as the corporate audit executive (CAE); as well as leading the offices of Ethics and Business Conduct; Environment, Safety, and Health; enterprise risk; and serving as chief sustainability officer.

[8] Previously, Mackay chaired the Board of Visitors at the Graduate School of Public Affairs of the University of Maryland (2008–2014).

He was concentrated on the CARES project, a capital asset realignment of VHA; enhanced use leasing; lowering the backlog of pending veterans' claims; achievement and maintenance of a clean audit; the National Shrine Commitment, an effort to raise, and make standard, the condition of the national cemeteries; and VetFran, a program for transitioning veterans to aid them in starting franchise businesses.

He was also, with David Chu, a founding co-chair of the VA-DoD Joint Executive Council to increase interdepartmental collaboration and sharing.

Upon his departure, then-Secretary Anthony Principi stated, "Dr. Mackay brought to VA the discipline of the business world and the compassion of a man who cares deeply for America's veterans.

"[11] From 1993 to 1995, Mackay served as military assistant to then-Assistant Secretary of Defense for International Security Policy, Ashton Carter.

[12] During this time, the office was re-organized to focus on cooperative de-nuclearization, execution of the Nunn-Lugar threat reduction program, nuclear weapons policy, and counter-proliferation.

In 2005, Mackay was awarded a Doctor of Laws, honoris causa from Concordia Seminary, and served as the commencement speaker for its graduation that year.