The Cardassian sector was a region of space. This sector was patrolled by Cardassian patrol ships. This sector was adjacent to Sector 21503.
In 2367 the USS Enterprise-D was on a mapping survey near this sector. (TNG: "The Wounded", "The Mind's Eye")
The planet Draygo IV was located 3.7 light years from Cardassian space in this sector. (TNG: "Homeward")
This sector was only mentioned in dialogue.
According to the script, the pronunciation for Cardassian was "car-DASS-ee-en".