3rd Battalion (Airborne), 509th Infantry Regiment
3rd Airborne Battalion Combat Team, 509th Infantry Regiment
3rd Battalion, 509th Infantry Regiment
3rd Battalion, 509th Parachute Infantry Regiment
"Geronimo"

The mission of the 3rd Battalion (Airborne), 509th Infantry Regiment is to, on order, deploy world-wide to conduct an airborne assault, offensive operations, and/or counter-insurgency operations in support of the global contingency operations.

The distinctive unit insignia was originally approved on 30 September 1963. It was amended on 18 November 1963 to correct the wording of the blazon. The stylized yellow (gold) figure of a parachutist on a black ground was adapted from the device worn by the 501st Parachute Infantry Regiment during World War II and by which it was known throughout the Mediterranean Theater. The red field alluded to the red berets worn by the British 1st Airborne Division and the close association between it and the Regiment during World War II in England and North Africa. The nebuly (heraldic delineation for water) white and blue bars (the colors blue and white are used for Infantry) referred to the record breaking parachute flight from England to North Africa on 8 November 1942. The 2 segments of the wavy blue bar simulate the streamers of the Distinguished Unit Citations awarded for the gallant actions at Carano, Italy and Liege, Belgium, and in being a heraldic symbol of water referred to the amphibious landing on the Anzio-Nettuno beachhead on 22 January 1944. The black pile simulated a parachute jump and in also being a heraldic symbol used frequently for Engineers, the 2 sides referred to the ground defense the organization participated in during the Anzio and Ardennes-Alsace (Battle of the Bulge) Campaigns. The 5 arrowheads were for the 5 assault landings made by the 501st Parachute Infantry Regiment in World War II.

The 1st Battalion (Airborne), 501st Infantry Regiment was first constituted on 14 March 1941 in the Army of the United States as Company C, 504th Parachute Battalion and activated on 5 October 1941 at Fort Benning, Georgia. The unit was reorganized and redesignated on 24 February 1942 as Company F, 503rd Parachute Infantry, on 2 November 1942 as Company F, 509th Parachute Infantry, and on 10 December 1943 as Company C, 509th Parachute Infantry Battalion. The unit participated in 8 campaigns in the Second World War: Algeria-French Morocco (with arrowhead indicating participation in the initial assault), Tunisia (with arrowhead), Naples-Foggia (with arrowhead), Anzio (with arrowhead), Rome-Arno, Southern France (with arrowhead), Rhineland, and Ardennes-Alsace. The unit was disbanded on 1 March 1945 in France.

The unit was reconstituted on 12 May 1947 in the Regular Army as Company C, 509th Parachute Infantry Battalion. It was redesignated on 1 April 1963 as Headquarters and Headquarters Company, 3rd Battalion, 509th Infantry. Its organic elements were constituted on 15 January 1972.

The Battalion was activated on 15 January 1973 in Germany. As the war in Southeast Asia drew down, forces began to return to US Army Europe (USAREUR). The 1st and 2nd Battalions of the 509th Infantry were designated as dual-capable, mechanized and airborne. They were later discontinued and replaced with 2 battalions (2-28th Infantry and 2-87th Infantry), which brought the 8th Infantry Division to fully mechanized status and provided it with the ability to defend Central Europe, its primary task. To provide greater mobility to the Mediterranean area, the 3-509th Infantry was reflagged as the 1st Battalion, 509th Infantry, an Airborne Battalion Combat Team, and assigned to Italy. It was inactivated on 31 August 1973 in Italy.

Headquarters and Headquarters Company, 3rd Battalion, 509th Infantry was redesignated on 1 July 1975 as Company C, 509th Infantry, and activated at Fort Rucker, Alabama. The unit was transferred on 2 October 1988 to the United States Army Training and Doctrine Command and reorganized at Fort Rucker, Alabama. It was inactivated on 31 May 1993 at Fort Rucker, Alabama, and withdrawn from the United States Army Training and Doctrine Command.

The unit was redesignated on 10 September 2004 as Headquarters and Headquarters Company, 3rd Battalion, 509th Infantry. The Battalion was assigned on 16 September 2005 to the 4th Brigade Combat Team, 25th Infantry Division, and activated at Fort Richardson, Alaska. It was redesignated on 1 October 2005 as the 3rd Battalion, 509th Infantry Regiment.