Blue Horizon was a planet located somewhere in the space of the galaxy's Alpha or Beta Quadrants. A terraformed planet created by Gideon Seyetik, Blue Horizon was the site of a Federation colony. Michelle Culhane killed two people in the Blue Horizon colony. Culhane commented to Kyle Riker that Blue Horizon was a "lovely place, but bad things can still happen in nice surroundings". (ST - The Lost Era novel: Deny Thy Father) In 2369, Benjamin Sisko and his son Jake Sisko visited Blue Horizon on the way to Deep Space 9. (DS9 episode: "Second Sight")