The Cuellar system (pronounced KWAY-yar) was a star system located in Sector 21505 that was situated within in Cardassian space. The system had a good strategic position to be used for an invasion of three Federation sectors alongside the Cardassian border.
A Cardassian space station was located in the system until it was incinerated by the USS Phoenix in 2367. The Cardassians claimed it to be a science station, but Captain Benjamin Maxwell of the Phoenix claimed, that there was nothing of scientific interest in the system and considered it a military transport station. (TNG: "The Wounded")