Perimeter Action Group 21 (also known as PA Group 21) was a Starfleet battle force extant in the late 23rd century. (Ships of the Star Fleet, vol. 2)
PA Group 21 consisted of USS Brant, USS Artika and other vessels. In the early 2290s, the group was homeported at Starbase 14.
- Perimeter action groups may have been the counterpart of what were called pursuit groups in other continuities.