15th Regiment
- 15 Squadron (disambiguation)
- 15th Alabama Infantry Regiment
- 15th Army (disambiguation)
- 15th Brigade (disambiguation)
- 15th Connecticut Infantry Regiment
- 15th Continental Regiment
- 15th Division (disambiguation)
- 15th Field Artillery Regiment (Canada)
- 15th Group (disambiguation)
- 15th Guards Motor Rifle Regiment
- 15th Illinois Cavalry Regiment
- 15th Illinois Infantry Regiment
- 15th Infantry Regiment (South Korea)
- 15th Infantry Regiment (United States)
- 15th Iowa Infantry Regiment
- 15th Massachusetts Infantry Regiment
- 15th Massachusetts Regiment
- 15th New York National Guard Regiment
- 15th Poznań Uhlan Regiment
- 15th Regiment of Foot
- 15th South Carolina Infantry Regiment
- 15th Virginia Regiment
- 15th West Virginia Infantry Regiment
- 15th Wing (disambiguation)
- 15th Wisconsin Infantry Regiment
- United States Army Forces in the Philippines – Northern Luzon
- XV Corps (disambiguation)