James Smith "Mac" McDonnell (April 9, 1899 – August 22, 1980) was an American aviator, engineer, and businessman.

After graduating from MIT, he was hired by Thomas Towle for the Stout Metal Airplane Division of the Ford Motor Company.

This aircraft then competed in a safe airplane contest which was sponsored by the Daniel Guggenheim Fund for the Promotion of Aeronautics and which offered a $100,000 prize for the winning entry.

[4][5][6] After the failure of the Doodle Bug to win the contest (the Curtiss Tanager won) or any commercial orders due to the Great Depression, he dissolved his firm and worked for the Great Lakes Aircraft Company in 1931 before he was hired as an engineer for the Glenn L. Martin Company.

Headquartered in St. Louis, the company quickly grew into a principal supplier of fighter aircraft to the U.S. Air Force and U.S. Navy—including the F-4 Phantom II—and built the Mercury and Gemini space capsules.

[10] McDonnell Hall, housing part of the physics department at his alma mater, Princeton, also bears his name and an airplane-inspired design.

Among the Princeton faculty members who have held the professorship are Val Fitch, Joseph Taylor, Anne Treisman, Curtis G. Callan, Lyman A.