The Coalition of Madena was an interplanetary alliance of two inhabited planets in the Omega Sagitta system, Atlec and Straleb. Both worlds were populated by a humanoid race who colonized the system during the 22nd century, and co-existed, according to Jean-Luc Picard, "under a precarious but successful treaty."
The two worlds were technically at peace, but relations were severely strained until 2365, when Benzan of Straleb and Yanar of Atlec, both children of the respective leaders of each world, became engaged. (TNG: "The Outrageous Okona").
Straleb appeared in the star chart Data and Picard were studying in stellar cartography in 2371. (Star Trek Generations)
In Generations, Straleb was identified as Straleb Madena.
In the episode's script, this alliance was described as the "coalition of Madena VI."