The 503rd Infantry Regiment, formerly the 503rd Parachute Infantry Regiment and the 503rd Airborne Infantry Regiment, is an airborne infantry regiment of the United States Army. The regiment served as an independent regiment in the Pacific War during World War II; at Fort Campbell, Kentucky; in Okinawa, Japan; and in Germany. Regimental elements have been assigned to the 2nd Infantry Division, the 11th Airborne Division, the 24th Infantry Division, 25th Infantry Division, the 82nd Airborne Division, 101st Airborne Division, and the 173rd Airborne Brigade Combat Team. Regimental elements have participated in campaigns in the Vietnam War, Operation Enduring Freedom–Afghanistan, and Operation Iraqi Freedom. The regiment claims 15 Medal of Honor recipients: two from World War II, ten from Vietnam, and three from Afghanistan. A parent regiment under the U.S. Army Regimental System. The regiment's 1st and 2nd Battalions are active, assigned to the 173rd Airborne Brigade, based at Caserma Ederle, Vicenza, Italy. The 3rd and 4th Battalions as well as Companies E, F, G, H, and I have been inactived.

The 2nd Raiding Brigade, also known as the Takachiho Paratroopers, was an Imperial Japanese airborne forces unit. Part of the Imperial Japanese Army Air Service (IJAAS), the unit was notably involved in the Battle of the Philippines in 1945, during which it was almost completely destroyed.