The 506th Infantry Regiment, originally designated the 506th Parachute Infantry Regiment (506th PIR) during World War II, is an airborne light infantry regiment of the United States Army. Currently a parent regiment under the U.S. Army Regimental System, the regiment has two active battalions: the 1st Battalion, 506th Infantry Regiment (1-506th IR) is assigned to the 1st Brigade Combat Team, 101st Airborne Division, and the 2nd Battalion, 506th Infantry Regiment (2-506th IR) is assigned to the 3rd Brigade Combat Team, 101st Airborne Division.