Longin Hieronim Pastusiak (pronounced [ˈlɔnɡin pasˈtuɕak]; 22 August 1935 – 10 January 2025) was a Polish politician and historian.

In 1959 Pastusiak earned his Master of Arts degree from Woodrow Wilson School of Public and International Affairs, University of Virginia in Charlottesville.

In 1967 he earned the title of Doctor Habilitated from the Institute of History, Polish Academy of Sciences.

Pastusiak was in 2008 a visiting professor at Appalachian State University in Boone, North Carolina.

Since 1998 he was Vice-chairman of the International Council of the organisation Parliamentarians for Global Action based in New York.

From 2002 to 2004, Pastusiak served as vice president of NATO Parliament Assembly and from 2001 until 2005 he was Marshal of the Senate of the Polish Republic.