Vincent Peter Mroz (March 11, 1922 – July 22, 2008) was a United States Secret Service agent and a United States Marine Corps veteran who served during World War II. In 1948, he was assigned to the presidential protection detail during the Harry S. Truman administration. In November 1950, Mroz shot one of two Puerto Rican nationalists who intended to assassinate President Truman. The man was later tried and imprisoned. The event was described as "the biggest gunfight in Secret Service history." The other nationalist was killed by a city police officer.