Sector 21505 was a region of space. This Cardassian sector contained the Cuellar and Kelrabi systems.

In 2367, the rogue starship USS Phoenix assaulted several targets in this sector, including a research station in the Cuellar system. The USS Enterprise-D entered this region by order of Starfleet to assist the Cardassians in locating the Phoenix. The Phoenix successfully destroyed two Cardassian ships before it was stopped by the Enterprise-D. ({{TNG|The Wounded})

This sector was only mentioned in dialogue.