506th may refer to:

• 506th Air Expeditionary Group, provisional United States Air Force unit
• 506th Air Refueling Squadron, inactive United States Air Force unit
• 506th Airborne Infantry Regiment Association, charitable veterans' organization
• 506th Bombardment Squadron, inactive United States Air Force unit
• 506th Fighter Squadron, unit of the Oklahoma Air National Guard that flies the KC-135 Stratotanker
• 506th Infantry Regiment (United States), unit assigned to the 4th Brigade Combat Team (BCT) of the 101st Airborne Division

• 506 (number)
• 506, the year 506 (DVI) of the Julian calendar
• 506 BC
• E Company, 506th Infantry Regiment (United States), one of the best-known companies in the United States Army