The Argolis Cluster is a region of space in the Alpha Quadrant containing a number of protostars, as well as the planet Tagra IV.
The Argolis Cluster was situated close to Cardassian territory, and was a strategic site during the Dominion War. (TNG episodes: "I, Borg", "True Q", DS9 episodes: "Behind the Lines", "The Reckoning")
One planet in the Argolis Cluster had been colonized by Earth prior to the 2370s decade, and had lost contact with the Federation. (DS9 novel: ...Sacrifice of Angels)
In the year 2305, a shuttlecraft carrying Lieutenant Arex Na Eth encountered a black hole in the Argolis Cluster, flinging him seventy-one years forward to 2376. (NF short story: "The Road to Edos")