Pentath III was the third planet in the Pentath system, and a member of the Cardassian Union.

Pentath III was one of many Cardassian planets whose infrastructure was devastated by the Klingon invasion of 2372. An outbreak of Rudellian plague there prompted the Detapa Council to dispatch several relief convoys to the planet. Due to the lack of Cardassian fleet resources, the Council requested Starfleet escorts for the convoys. The USS Defiant was one of the starships assigned to this mission. (DS9: "Rules of Engagement")