The 513th Parachute Infantry Regiment (513th PIR) was an airborne infantry regiment of the United States Army, raised during World War II. The 513th formed part of the 17th Airborne Division and participated in the European Campaign, fighting in the latter stages of the Battle of the Bulge in January 1945 and parachuted into Germany in Operation Varsity in March, in the largest airborne drop of the war. The regiment returned to the United States in September 1945 where it was inactivated.