The Almatha sector was a sector in the Cardassian Union which bordered both the Bajor sector and the border with the United Federation of Planets.
The sector was named after Almatha, one of the stars located there. (ST website: StarTrek.com)
In 2371, the Maquis used a ship to create a perimeter alert in the Almatha sector to distract the Cardassians from Tom Riker and the USS Defiant's real target. (DS9 episode: "Defiant")
In 2377, Ensign Prynn Tenmei sabotaged the USS Euphrates on the border between the Bajor sector and the Almatha sector. (DS9 novel: Warpath)
The Almatha sector was controlled by the Cardassians in the mirror universe. (DS9 - Mirror Universe novel: Saturn's Children)